The Collaborative International Dictionary of English v.0.48:

Plica \Pli"ca\, n. [LL., a fold, fr. L. plicare to fold. See
   Ply, v.]
   1. (Med.) A disease of the hair (Plica polonica), in which it
      becomes twisted and matted together. The disease is of
      Polish origin, and is hence called also Polish plait.
      --Dunglison.
      [1913 Webster]

   2. (Bot.) A diseased state in plants in which there is an
      excessive development of small entangled twigs, instead of
      ordinary branches.
      [1913 Webster]

   3. (Zool.) The bend of the wing of a bird.
      [1913 Webster] Plicate

WordNet (r) 3.0 (2006):

plica
    n 1: a folded part (as in skin or muscle) [syn: fold, plica]