bullpen -
An enclosed area for pitchers to warm up in during a game.
bullpen -
The relief pitchers of a team collectively.
bullpen -
Metaphorical A figurative place for someone or something to get ready.
bullpen -
An open seating arrangement where project teams can communicate openly with minimal effort.
Wikipedia
The bullpen (or simply the pen) is the area where relief pitchers warm-up before entering a game. Depending on the ballpark, it may be situated in foul territory along the baselines or just beyond the outfield fence. Also, a team's roster of relief pitchers is metonymically referred to as "the bullpen".