Among ballplayers, an abbreviation for batting practice. Pronounced just like the letters. Batting practice usually starts soon after the gates to the park officially open, and on off-days when the team isn't travelling. A big cage is erected around the plate, and the pitcher, usually a coach or a rehabbing pitcher, throws off the mound from behind a screen, with the intent of throwing pitches to hit. Good batting practice pitchers get rewarded with trips to the All-Star Game to pitch bp during the Home Run Contest. Some examples of usage:

     "Nomar always shows up to the ballpark early to get some extra BP in."

     "Dravecky threw BP yesterday, but it will be some time before he returns to the Giants' rotation."

     "The fans at Busch Stadium were delighted by Mark McGwire's gargantuan blasts during the Cardinals' pre-game BP session."

     "The way Lima's pitching tonight, it's gotta be like BP for these Mets hitters."