Source : Webster's Revised Unabridged Dictionary (1913)

Labellum \La*bel"lum\, n.; pl. L. {Labella}, E. {Labellums}.
   [L., dim. of labrum lip.]
   1. (Bot.) The lower or apparently anterior petal of an
      orchidaceous flower, often of a very curious shape.

   2. (Zo["o]l.) A small appendage beneath the upper lip or
      labrum of certain insects.