a bottomless, boxlike, usually glass-covered structure and the bed of earth it covers, heated typically by fermenting manure or electrical cables, for growing plants out of season.

a place or environment favoring rapid growth or spread, esp. of something disliked or unwanted

a hotbed of disease.

Slang . a bed shared by two or more persons in shifts, each sleeping in it for or at a designated time and then vacating it for the next occupant.

Slang . to share a bed in shifts, so that it is always occupied.