n. (pl. s) 1 a upper covering of a building. b top of a covered vehicle. c top inner surface of an oven. refrigerator, etc. 2 overhead rock in a cave or mine etc. v. 1 (often foil. by in. over) cover with or as with a roof. 2 be the roof of. o go through the roof colloq. (of prices etc.) rise dramatically. hit (or go through) the roof colloq. become very angry. [Old English]