\La"bi*um\, n.; pl. L. {Labia}, E. {Labiums}. [L.]
1. A lip, or liplike organ.
2. The lip of an organ pipe.
3. pl. (Anat.) The folds of integument at the opening of the
   vulva.
4. (Zo["o]l.)
   (a) The organ of insects which covers the mouth beneath,
       and serves as an under lip. It consists of the second
       pair of maxill[ae], usually closely united in the
       middle line, but bearing a pair of palpi in most
       insects. It often consists of a thin anterior part
       (ligula or palpiger) and a firmer posterior plate
       (mentum).
   (b) Inner margin of the aperture of a shell.