The Collaborative International Dictionary of English v.0.48:
Pleuron \Pleu"ron\, n.; pl. Pleura. [NL., fr. Gr. ? a rib.] (Zool.) (a) One of the sides of an animal. (b) One of the lateral pieces of a somite of an insect. (c) One of lateral processes of a somite of a crustacean. [1913 Webster]