an enclosure, cage, or pen, usually with bars or wires, in which fowls or other small animals are confined for fattening, transportation, etc.

any small or narrow place.

Slang . a prison.

Sometimes Facetious . a cooperative, esp. the cooperative bookstore of a college or university.

to place in or as if in a coop; confine narrowly (often fol. by up or in ).

Slang . (of a police officer) to park and sleep inside one's patrol car while on duty. ?

fly the coop

Informal . to run off; depart abruptly; escape

We stopped to see my sister, but she'd flown the coop.