Roof  —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 foll. By in, over) cover with or as with a roof. 2 be the roof of.  go through the roof colloq. (of prices etc.) Rise dramatically. Hit (or go through) the roof colloq. Become very angry. [old english]