in·mate (ĭn'māt') n. A resident of a dwelling that houses a number of occupants, especially a person confined to an institution, such as a prison or hospital.
1589, "one allowed to live in a house rented by another" (usually for a consideration), from in "inside" + mate "companion." Sense of "one confined to an institution" is first attested 1834.
Main Entry: in·mate Pronunciation: 'in-"mAt Function: noun : one of a group occupying a single place of residence; especially: aperson confined (as in a psychiatric hospital) especially for a long time