BULLPEN
bullpen, detention cell, detention centre
(noun) a large cell where prisoners (people awaiting trial or sentence or refugees or illegal immigrants) are confined together temporarily
bullpen
(noun) a place on a baseball field where relief pitchers can warm up during a game
Source: WordNet® 3.1
Etymology
Noun
bullpen (plural bullpens)
An enclosed area used to hold bulls.
(baseball) An enclosed area for pitchers to warm up in during a game.
(baseball) The relief pitchers of a team collectively.
(figurative) A place for someone or something to get ready.
An open seating arrangement where project teams can communicate openly with minimal effort.
Source: Wiktionary