cell vs bullpen

cell and bullpen both are nouns.

Word	Noun	Adjective	Verb	Adverb
cell	Yes	No	No	No
bullpen	Yes	No	No	No

As nouns, bullpen is a hyponym of cell; that is, bullpen is a word with a more specific, narrower meaning than cell:

cell: a room where a prisoner is kept
bullpen: a large cell where prisoners (people awaiting trial or sentence or refugees or illegal immigrants) are confined together temporarily

Other hyponyms of cell include detention cell, detention centre, cooler, tank, dungeon, guardroom, hold, keep, sweatbox.

cell (noun)	bullpen (noun)
(biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals	a large cell where prisoners (people awaiting trial or sentence or refugees or illegal immigrants) are confined together temporarily
a device that delivers an electric current as the result of a chemical reaction	a place on a baseball field where relief pitchers can warm up during a game
a room where a prisoner is kept
small room in which a monk or nun lives
any small compartment
a hand-held mobile radiotelephone for use in an area divided into small sections, each with its own short-range transmitter/receiver
a small unit serving as part of or as the nucleus of a larger political movement