- ☆ bullpen [bool′pen΄ ]n.1. a fenced enclosure for bulls2. Informal a large room or enclosure for a number of people; specif., a barred enclosure in a jail, where prisoners are kept together temporarily, as between their arrest and the placing of charges3. Baseballa) an area near the playing field, where relief pitchers practice and warm upb) the relief pitchers of one team
English World dictionary. V. Neufeldt. 2014.