I've spent most of my life playing or being around baseball. With college and high school teams already playing a month and a half and MLB having started their season a few days ago there is a language most people don't understand but will commonly hear during games. You'll hear these from coaches, players, and commentators but most will be used by high school through minor league players.
Ace — the best pitcher on a team who gets extra special treatment from coaches in the lower levels of play.
Alley — the best place to hit a ball in the outfield where it drops between the outfielders. Best hits are line drives that hit and roll through the alley to the wall, commonly resulting in a double or triple and in rare occasions an inside-the-park home run.
Around the Horn — a double play that starts at third going around the infield to second then to first. Can sometimes be a triple play where the third baseman steps on third before throwing to second.
Backdoor Slider — a pitch that starts out or appears out of the strike zone that breaks into the strike zone. Typically thrown as the third strike to get a player to hack at it to strike out swinging or to get caught looking.
Bad Hop — when you go to field a ball and it hits the ground and curves away from you or bounces over you.
Baltimore Chop — a ball hit that goes almost straight down hit hard enough and at a decent angle to hit home plate or in front of home plate but bounces into the outfield over the infielders.
Bang Bang — a play where the runner hits the bag right before the ball or where the ball reaches the fielder's glove right before the player reaches base.
Basket Catch — when a fielder, typically an outfielder, catches a ball in an upturn position around the belt. Usually when a fielder has his back to the ball and is running towards the wall.
Bat Flip — a cocky move when you hit a dinger and toss your bat in different fashions to assert dominance towards the pitcher. Best when the opposing team is in the first base dugout.
Bean or Beaner — a pitch, most commonly a fastball that hits a batter in the head.
Bench Clearer or Bench Clearing Brawl — when there's a fight and the benches and bullpen run out to help. Typically just to assert dominance towards the other team and rarely are they ever good fights.
Big Dick Energy — having the confidence to know you're gonna take a pitcher 450 dead center but staying cool and not having the cockiness to talk trash beforehand. Not the kind to do a bat flip or talk trash but to still have his presence known.
Blue — refers to the umps or umpires and usually a derogatory term often combined with a phrase calling them blind.
BP — no not the oil. BP is batting practice where players, especially in Bush League or lower, have dinger derbies.
Brusher or Brushback — an inside pitch that doesn't hit a batter but makes them jump back or drop to the ground. Typically an intimidation move by the pitcher to assert dominance or to back the batter off the plate.
Bush — to make an amateur play or to act amateurish and not like you're a pro.
Bush League — lower levels of the minors such as Single A, Single A Short, and sometimes Double A.
Camping — when a ball is hit as a popup and the player is just waiting for the ball to come back to Earth, typically followed by a can of corn catch.
Can of Corn — typically said as "Canna Corn" is a catch a baby could make with or without a glove. Most commonly is a popup that is hit where the fielder is already standing and just camps under it.
Caught Looking — when a third strike is thrown and the batter stands there watching it.
Caught Napping — when a baserunner is thrown out either by not paying attention or reacts too late.
Cellar — when you're in dead last for your division. Honestly at that point why show up to games.
Cheddar — refers to either a pitcher throwing good pitches to have a dinger derby or when the coach is throwing perfect pitches at BP to hit cage bombs or yet again have a dinger derby.
Cheese — a sexy fastball to a batter where he can go 450 Dead Center on a pitcher. Sometimes refers to a good fastball that flies right past the batter for a strike.
Chinner or Chin Music — a very high and inside pitch that buzzes close to the batters chin.
Circus or Circus Catch — a web gem catch either on a sacrifice your body type of catch or acrobatic jumping catch followed by a summersault. Pretty much outfielders attempting to show off because they just sit out in the outfield bored most of the game.
Cycle — the greatest feat you can do as a batter where you hit a single, double, triple, and dinger all in the same game.
Daddy Hack — a swing that takes all your power and throws you on your ass. The batter swings envisioning a dinger but usually does a daddy hack on a third strike breaking ball.
Dinger — a homer that is destined for the moon maybe even another solar system that you just sit and salute as it flies and then assert your dominance on the pitcher with your cockiest bat flip and jog around the bases as you talk trash the whole time.
Dinger Derby — refers to BP where players are hitting nothing but dingers or to a game where the pitcher is throwing cheddar and batters are hitting nothing but dingers.
Dirty — one of the ways you can say something's nice. Honestly, baseball players can use so many words to equal that's nice.
Filthy — used to refer to anything that looks good such as a hit, a haircut, an accessory, etc. Just another way to say something's nice while using a word that typically means unclean.
Fireman — a closer who can typically throw a scary fast heater and leave you scratching your head in the breeze off of it.
Five Tool Player — a guy who can do everything and do it perfectly such as fielding, hitting, hitting power, throwing, and running.
Frozen Rope — a well-hit line drive. If playing third it was nice knowing you when one comes to the hot corner.
Fungo — a type of bat used by coaches during fielding practice that makes the balls go semi-crazy when hit but provides fielders a chance to do a web gem.
Gap — essentially the same as an alley. The best place in the outfield to hit a ball.
Get Bucket — at the end of BP or during BP someone has to pick up all the balls and put them in a bucket. Sucks to suck if your a freshman or a rookie.
Golden Sombrero — when a batter strikes out four times in a game. You never want to be the player wearing the golden sombrero.
Good Game — if you don't know then you aren't one of the trusted ones with this butt slap and grab ceremony and no it's no homo.
Go Yard — to hit a dinger 450 dead center while making your cockiness and dominance known.
Heat — when a pitcher, typically a fireman, is throwing primarily heaters to assert his dominance as you stand and watch or duck away till you strike out and go cry in the dugout.
Heater — a four-seam fastball in the upper 90s going up to 105 or 106. Pitches if you're able to hit will go for dingers as your bat explodes to show your dominance, if not definitely a good pitch for the pitcher to show his.
Hot Corner — refers to Third Base where especially right-handed will pull a ball hard towards third down the line. If playing third and a line drive comes your way you better catch it.
In the Hole — not the batter in the on-deck circle but the batter after him.
Jacked — a player that's probably on roids because he's so big or got big fast.
Jam — when a pitcher gets into a situation usually with players on base, one or no outs, and is behind in the count with a batter.
Jammed or Jammer — when you hit the ball with the handle of the bat rather than the barrel, typically on a high and inside pitch that sends a shock starting at your hands going through the rest of your body. Can also refer to a tight swing on a high and inside pitch where you can barely swing but still get a hit.
Meatball — a juicy fastball that hangs right down the middle and is an easy hit typically for a dinger.
Mendoza Line — a line around the .200 batting average in which you never want to drop under or else you legally suck. Named after Mario Mendoza who was one of the leagues worst hitters.
Moon Shot or Moon Blast — a dinger that is hit very high like it's a rocket on its way to the moon.
Ofer or O for — someone who didn't get a hit in a game but grounded or flied out so he can't wear the golden sombrero.
Pegged — to get hit hard by a pitch that will definitely leave a bruise.
Pepper — a fielding game where players catch a hit ball and throw it to the hitter so he can hit their throw. Only for the brave.
Phiten — necklace and bracelet company that players swear gives them superpowers. But for the most part, it's just another form of swag.
Pickle — when trapped between two bases in a rundown. If you have moves you might be good if not just stand there and take it like a man.
Pimped It — to destroy a ball on a good hit typically for a liner or a dinger.
Roids — Steroids or also called juice is commonly used in baseball to get that extra power or edge.
Rhubarb — a fight. Typically doesn't last long but sometimes a good punch is thrown. Best is when there's a bench-clearing brawl.
Seeing Eye Single — a ball hit between infielders typically picked up by an outfielder but gives enough time for a runner to reach first.
Shagger — someone who goes to pick up foul balls or dingers hit in BP so there's still balls to hit. Again sucks to suck if your a freshman or rookie.
Shoestring — a catch made around the shins to the foot before the ball hits the ground.
Stroking — to hit good, whether in a game or at BP. More than likely BP where you get too cocky.
Table Setter — a leadoff or number two guy that is generally a faster player who is just to get a runner on base so a power hitter can drive them in.
Tape — whether it's athletic or batting tape, either is the duct tape for players respecting it like the God it is.
Tape Measure — a dinger that isn't always a high hit homer like a moon blast but is hit out of the park and far enough to say let's get out the tape measure.
Tommy Johns — a surgery to add a tendon from the knee to one's elbow to make the UCL stronger for throwing.
Ugly Finder — a foul ball typically hit during BP that goes straight for a player who usually is not prepared. Can refer to a foul ball that goes straight into the dugout during a game. Either way, if it hits your face, even if you were pretty before, you aren't now.
Wheelhouse — a pitch to the batters hot zone typically waist high and dead center of the plate that typically results in a good liner or dinger.
Yakker — a very good curveball that leaves them daddy hacking or caught just looking. Best Yakkers are curves thrown by a lefty.
Yoked — being a huge probably on roids player who is straight jacked.
Those are some of my favorites but in the game of baseball, the terms change all the time. There are terms from the old days that remain but some might be forgotten for some new term that has more swag to it because baseball is all about the swag.