labrum /ˈleɪ.bɹəm/ noun3 •The uppermost of the mouthparts (trophi) of a typical insect, such as a cockroach. Typically resembles an upper lip and forms part of the roof of the mouth in such insects. •Any of several lip-like projections. •A large basin of warm water, with an overhanging lip, in a Roman bath. formslabra · labrums