Labellum \La*bel"lum\ (l[.a]*b[e^]l"l[u^]m), n.; pl. L. {Labella} (l[.a]*b[e^]l"l[.a]), E. {Labellums} (l[.a]*b[e^]l"l[u^]mz). [L., dim. of labrum lip.] 1. (Bot.) The lower or apparently anterior petal of an orchidaceous flower, often of a very curious shape. [1913 Webster] 2. (Zool.) A small appendage beneath the upper lip or labrum of certain insects. [1913 Webster]