aboard - a runner reaching base.
ace - the star pitcher on a team.
appeal - a claim by the fielding side to an umpire that a rules violation has taken place.
assist - if a fielder throws the ball to another fielder who makes an out, he's credited with an assist.
at bat - an appearance by a hitter.
backstop - a barrier behind home plate to stop the ball if the catcher misses it.
balk - if the pitcher doesn't pitch when he's started his pitching motion, it's a balk and runners are awarded an extra base.
ball - a pitch which is called outside the strike zone, and which the hitter doesn't try and swing at.
ball park - a baseball field.
base - the square bag located at each corner of the infield.
base coaches - when a team is batting, a coach is allowed to occupy a box close to first and third bases.
base hit - a hit which allows the batter to reach first, second, third or home base, unless on a "fielder's choice".
baseman - the fielders positioned near to first, second and third base.
base on balls - if the pitcher throws four balls, the hitter is awarded a free "walk" to first base.
base paths - the areas between the base pads are marked out with dirt. A runner cannot run outside the base paths to avoid a tag.
bases loaded - runners on first, second and third bases.
batting around (the order) - an inning in which all nine hitters appear at the plate without three outs being made.
bat boy - a person employed to run on and collect the hitter's bat when he drops it to start running.
batter - the member of the hitting team currently at the plate.
batter's box - either side of home plate is a batter's box, in which the batter has to stand when he tries to hit the baseball.
batting order - the order in which the hitter's take their turn to come up and bat.
beanball - a pitch thrown at the hitter's head (this is illegal).
benches clearing - all of the players from both sides leaving the benches (usually for a brawl!).
big leagues (or "the bigs") - major league baseball.
bleachers - the cheap seats in the outfield, furthest away from the main action.
bloop - a softly hit, or mis-hit, fly ball which goes over the infield but short of the outfielders for a base hit (e.g. "bloop single").
boot - an error by a fielder where instead of gathering the ball at his feet he accidentally kicks it away or knocks it away with the heel of his glove.
bottom half of the inning - the half-inning of the second team (always the home team).
breaking ball - a pitch that moves into, away from or suddenly drops as it reaches the hitter.
breaking up a double play - a runner who slides hard into second (or third base) and whilst being put out himself, puts the thrower off sufficiently to prevent him throwing out a second runner at a different base.
broken bat - a bat which shatters when the ball is hit.
brush back pitch - a pitch thrown "inside" to force a hitter crowding the plate to back off.
bull pen - the area in which the relief pitchers warm-up as they prepare to enter the game.
bunt - an attempt to hit the ball by simply dropping it close to the hitter, usually as a surprise tactic.
called game - a game ended early by the umpire (for rain, etc).
called strike - a strike which is called by the umpire (as opposed to a swing and a miss).
caught looking - a third strike where the hitter doesn't even swing, looking in vain for a "ball".
change up - a slower pitch thrown with the same action as a fastball.
center field - the middle part of the outfield.
check swing - a false swing at a pitch, where the hitter starts swinging and then tries to stop.
chopper - a ball hit hard into the ground.
clean-up - the batter who hits fourth in the order (supposedly to hit a home run and clean up runners on other bases).
climbing the ladder - a pitcher throwing successive fast balls higher and higher in the strike zone.
closer - the relief pitcher who comes in late in the game to make the final few outs.
clutch - a player who performs at key moments.
coaches - the staff who assist the manager in running the team.
corked bat - a bat which has has been hollowed out, and cork substituted, to make home runs easier to hit. This is illegal.
count - the total number of balls and strikes against a hitter.
curveball - an off-speed breaking ball that drops sharply at the plate.
cut off man - an infielder who intercepts a throw from the outfield to relay it to whichever base he considers appropriate.
dead ball - a temporary break in play, indicated when an umpire calls "dead ball".
delivery - a pitcher throwing the ball to the hitter.
designated hitter - a hitter who bats instead of the pitcher in certain baseball leagues.
diamond - the name for the infield, marking out the four bases.
dinger - a home run.
disabled list (DL) - when a player is injured a team can place him on the "disabled list", freeing up a space on the roster without any penalty. A player placed on the DL must remain there for at least 15 days.
doctoring the ball - a pitcher doing something illegal to the ball to make it move more when he pitches.
double header - two games played on the same day, usually including a "make-up game" because of a previous postponement.
double steal - a play when two runners try to steal bases at the same time.
double - a base hit which allows the hitter to reach second base.
double play (DP) - a fielding play in which two offensive players are called out.
double play depth - a fielding alignment where the infielders field closer than usual, hoping to field a ground ball and throw out runners going to both second and first base.
down the pipe/middle - a pitch thrown in the middle of the strike zone.
drive in a run - a batter making a hit which brings a base runner in to score.
dug out - the area in which the players, manager and coaches sit when they aren't on the field of play or in the bullpen.
earned run - any run given up by a pitcher which was not the result of a fielding error.
earned run average (ERA) - the number of earned runs given up by a pitcher averaged over nine innings.
error - a fielding mistake which is officially charged against the fielder.
extra innings - if the score is tied after nine innings, then extra innings are played until the score is broken.
fair - a ball hit by the batter that stays within the foul lines between first and third base.
fast ball - a hard thrown pitch (sometimes as quick as 100 mph).
fighting off a pitch - a batter deliberately hitting a pitch foul to keep his at-bat alive.
fielder - a defensive player, the fielding team have nine fielders, one of whom is the pitcher.
fielder's choice - when the fielder allows the hitter to reach first base in order to throw out a runner at another base.
fielding average - a statistic calculated to show a fielder's efficiency.
fly ball - a ball hit into the air. If a fielder catches the ball, it's known as a "fly out".
force out - an out in which the runner is put out having been forced to run to a base.
fork ball - a split finger fastball, thrown with no wrist motion, that drops at the hitter's feet.
foul - a ball hit by the batter that falls outside of the foul lines between first and third base.
foul lines - the lines that extend from home base through first and third bases to the outfield walls.
foul poles - the poles that show where the foul lines meet the outfield wall. A ball has to hit or land inside of a foul pole to be a home run.
foul tip - a pitch that tips the bat and lands in the catcher's mitt - it counts as a strike.
full count - a count with three balls and two strikes.
gapper - a ball hit through a space between two outfielders and rolls all the way to the wall for extra bases.
glove - the glove fielders (except for the first baseman and catcher) wear on their non-throwing hand to catch the ball.
going around - the umpire ruling that a hitter has failed to check his swing and a strike should be called.
gopher ball - a pitch which gets blasted for a home run.
grab - a catch.
grand slam - a home run hit with the bases loaded (scoring four runs).
ground ball (or grounder) - a ball hit along the ground.
ground out - an out made when a fielder tags a runner or the base before the runner gets there.
ground rule double - a hit automatically awarded by the umpires when the ball lands fair and bounces out of play.
gunned down - a runner thrown out at a base.
heater/high heat - a fast ball.
hill - the pitcher's mound.
hit and run - a play in which the runner sets off early gambling on the batter making a base hit.
hitting for average - a hitter who focuses on hitting singles, and getting on base.
hitting for power - a hitter who focuses on extra base hits and/or home runs.
hitting for the cycle - a game in which a batter hits a single, a double, a triple and a home run.
hold - a middle relief pitcher who inherits the lead when he takes the mound, and still leads when he leaves it.
holding the runner - a baseman who stands close to a base, to prevent a runner from taking too big a lead away from the base.
home plate - the base located at home, over which a strike must be thrown and a runner must touch to score a run.
home plate umpire - the umpire at home plate, who calls strikes and balls.
home run - a hit over the outside wall, or which allows a runner to reach home base.
home stand - a series of home games played in succession.
hop - the bounce of the ball.
hanging pitch - a pitch that was meant to move sharply to confuse the hitter, but didn't.
in the hole - the area in which the short stop fields.
independent - a minor league ball club which isn't affiliated to any major league team.
infield - the area of the field inside the bases and base paths.
infield fly rule - the rule that prevents the fielding side from deliberately dropping an easy catch to then make a double-play.
infielder - a defensive player who fields in and around the infield.
innings - a game is divided into innings. Each team has nine innings in which to score runs. The visiting team hits in the "top of the inning" and the home team hits in the "bottom of the inning".
inning ending play - any play which results in the third out, ending an innings.
inside - a pitch thrown on the side of the plate closest to the hitter.
inside the park home run - a hit which allows the runner to reach home base without actually going over the outfield wall.
intentional walk - a base on balls deliberately given up by the pitcher for tactical reasons.
juiced - a term for a ball which has been doctored to make it more likely to get hit for a home run. Also now used to refer to a player who has done the same thing (through taking steroids!).
junking a game - a game in which a team effectively give up trying to win, saving themselves for the next game.
K - a strike out.
knuckle ball/knuckler - a slow pitch thrown with no spin that wobbles as it approaches the hitter.
LCS - League Championship Series.
LDS - League Divisional Series.
late movement/movement off the plate) - a pitch that deviates just as it's about to reach the hitter.
lead off batter - the first hitter in an inning.
left field - the side of the outfield behind third base.
left on base - a runner who is stranded on a base when the third out of the inning is made.
line drive - a batted ball which travels low and fast in the air.
line up - the batting order.
lit up - a pitcher who is getting hit almost every at bat (as in, "he lit up the scoreboard!).
long ball - a home run.
long relief - a pitcher who comes in early in a game to replace a struggling starting pitcher.
loss - a statistic allocated to whichever pitcher is considered to be most responsible for a game being lost.
major leagues (or "the majors") - The American League and the National League.
manager - the person in charge of the day-to-day running of the team.
middle relief - a relief pitcher who follows the starting pitcher and pitches in the "middle innings".
minor leagues (or "the minors") - the lower ranked leagues which form the farm system for the major leagues.
mitt - the more heavily padded glove the catcher and first baseman are allowed to wear, which has the four fingers combined into one unit.
night cap - the second game of a double header (even if it isn't played at night!).
no hitter - a game in which the pitcher does not concede a single base hit.
nubber - a mis-hit baseball which doesn't travel very fast.
numbers - statistics.
off the fists - a pitch that hits high up on the bat near the hitter's hands.
off the hook - a pitcher who expects to record a loss, and whose team score enough runs to tie the game, or take a lead.
official scorer - a statistician who records and determines the scoring for each game.
on base percentage - the proportion of plate appearances which lead to the hitter reaching base.
on deck - the batter who follows the hitter currently at the plate. He stands in the "on deck circle" warming up.
one hopper - a ball that bounces once before being fielded.
open base - a base with no runner on it.
out - when a hitter or runner is removed from the field of play by the fielding side.
outfield wall/fence - the wall or fence that marks the outer boundary of the field.
outfield - the area of the field beyond the infield.
outfielder - a fielder who occupies the outfield.
outside - a pitch thrown on the side of the plate away from the hitter.
painting the corners - a pitcher regularly locating his pitches at the edges of the strike-zone.
passed ball - a pitch not caught by the catcher, and considered to be the catcher's fault.
pen - the bull pen.
pennant (winning the) - the winner of a League Championship Series.
perfect game - a game in which the pitcher does not allow a single runner on base.
pick off - a runner who is caught too far off his base and tagged out without trying to steal a base or a base hit being made.
pinch hitter - a substitute hitter who comes into the game to replace another hitter.
pinch runner - a substitute runner who comes into the game to replace a base runner.
pitch - the throw made by a pitcher to the hitter.
pitcher's mound - the mound in the centre of the field from which the pitcher throws to the hitters.
pitcher's plate - a plate in the middle of the pitching mound with which the pitcher must be in contact whilst he pitches.
pitchout - a pitch deliberately thrown wide of the plate for a ball, to try and allow the catcher to throw out a stealing base runner.
plate - the base at home, over which pitchers have to throw the ball to get a strike.
play at the plate - a throw to home base which will arrive at the same time as a runner seeking to score.
play - the call made by the home plate umpire to start play.
pop up/pop fly - a fly ball in the infield.
power alleys - the spaces between the outfielders to which hitters will try and drive balls for doubles or triples (or even an inside-the-park home run).
power pitcher - a pitcher who mainly throws fastballs.
put out - an out made by a fielder.
rain delay - a delay in the game caused by rain.
rain out - a game cancelled because of rain.
RBI (runs batted in) - any time a hitter gets a hit, a base on balls, or sacrifices and a run scores, he's credited with an RBI. A batter can also be credited with an RBI on an ordinary, non-sacrifice out.
reliever - any pitcher who comes in after the starting pitcher.
retire the side - getting three outs and ending the inning.
retire in order - an inning where three hitters appear, and all three are retired.
right field - the side of the outfield behind first base.
road trip - a series of away games played in succession.
rookie - a player in his first full season in the major leagues.
rubber - the pitcher's plate.
rubber match - the deciding game of a three game series.
rundown - a runner caught between bases and chased down by two fielders to make a tag on him.
runners on the corners - base runners at first and third base (but not second).
sacrifice - a hitter deliberately sacrificing his out to advance at least one runner a base.
safe - a runner reaching base without being tagged.
save - when the final pitcher for a side inherits a narrow lead and retains it to ensure the win or pitchers for three or more innings in "effective relief" to finish a game.
scoring position - a base runner on second or third base, who can normally be expected to score on a single.
screwball - a curveball that moves into the hitter.
set up man - a pitcher who comes in to pitch before the closer.
seventh inning stretch - the period in the middle of the seventh inning, between the top and the bottom halves.
show ("the show") - the Major Leagues.
shutout (pitching a shutout) - a team whose opponents do not score a single run.
single - a base hit which allows the hitter to reach first base.
slide - an attempt to get on base where the runner goes in feet first (hook slide) or head first.
slider - a pitch that drops away from the hitter at the same time as moving away from him.
slugger - a hitter who tends to get extra base hits (including home runs).
slugging percentage - a statistic used to measure a batter's effectiveness at power hitting.
slump - a batter who has been struggling to hit over recent games.
solo - a home run hit with no runners on base.
south paw - a left handed pitcher.
split fingered fast ball - a pitch which looks like a fastball, but slower and which dips at the hitter.
squeeze play - a bunt on which a runner from third base tries to reach home base. On a "safety squeeze" the runner waits to see where the bunt goes before committing himself to, but on a "suicide squeeze" he takes off as the ball is pitched, which if the bunt goes wrong (or the hitter misses the bunt entirely) means it's suicide!
steal - a runner moving from one base to the next without the batter hitting the ball.
stopper - a starting pitcher relied on to win a game when his team may have lost a few games in a row.
stretch - the pitcher's set position for delivering the ball to home plate.
strike - a pitch which the umpire rules is within the strike zone, or swung at and missed by the hitter.
strike zone - the area above the hitter's knees, below the mid-point between the hitter's waist and shoulders, and over the plate.
strike out - an out where the pitcher retires the hitter with three strikes.
striking out the side - an inning where the pitchers strikes out all three batters.
swinging bunt - a hit in which the batter takes a full swing at a pitch, but only succeeds in hitting it a few feet, like a bunt.
swinging strike - a strike in which the hitter swings at a pitch and misses it.
tag - an out in which the fielder's catch a runner trying to reach base.
tagging up - a runner waiting on a base ready to run once a fly ball catch is completed.
taking a lead - a runner who inches away from a base to get a head-start on a base running attempt.
taking a pitch - a hitter not swinging at a pitch hoping it'll be a ball.
thrown away - a relay throw from a fielder which misses its target.
top half of the inning - the half inning of the first team (always the visiting team).
triple - a base hit which allows the hitter to reach third base.
unearned run - a run which scores as a consequence of an error (this isn't considered to be the "fault" of the pitcher).
walk - a "base on balls".
walk off - a home run scored in the bottom of the final inning to win the game.
warning track - a track in the outfield that marks that the wall is close by.
whiff - a swing and a miss.
wild pitch - a pitch not caught by the catcher, and considered to be the pitcher's fault.
win - a statistic credited to whichever pitcher is considered to be most responsible for a game being won.
wind up - the pitcher's motion in throwing to home base.