1. (Science: medicine) 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.
2. (Science: botany) A diseased state in plants in which there is an excessive development of small entangled twigs, instead of ordinary branches.
3. (Science: zoology) The bend of the wing of a bird.
Origin: LL, a fold, fr. L. Plicare to fold. See Ply.