bull pen

WordReference Random House Learner's Dictionary of American English © 2025

ˈbull ˌpen or ˈbullˌpen,n. [countable]

1. Sport
   • a place where relief pitchers warm up during a baseball game.
   • the relief pitchers on a team, considered as a whole:
     The bullpen is a little tired.
2. Informal Terms Informal.
   • a large cell for holding prisoners temporarily.

WordReference Random House Unabridged Dictionary of American English © 2025

bull′ pen′, 

1. Sport [Baseball.]
   • a place where relief pitchers warm up during a game.
   • the relief pitchers on a team.
2. Informal Terms
   • a large cell or room, usually next to the courtroom, where prisoners are temporarily held.
   • a large room in an office occupied by many employees.
3. any temporary or crowded quarters, as sleeping quarters in a lumber camp.
4. a pen for a bull or bulls.
Also, bull′pen′. 
• 1920–25 for def. 1 1800–10, American. for def. 4