‖Pin″na (?), n.; pl.Pinnæ (#), E. Pinnas (#). 1. (Bot.) (a) A leaflet of a pinnate leaf. See Illust. of Bipinnate leaf, under Bipinnate. (b) One of the primary divisions of a decompound leaf.
2. (Zoöl.) One of the divisions of a pinnate part or organ.
3. [L. pinna, akin to Gr. �.] (Zoöl.) Any species of Pinna, a genus of large bivalve mollusks found in all warm seas. The byssus consists of a large number of long, silky fibers, which have been used in manufacturing woven fabrics, as a curiosity.
4. (Anat.) The auricle of the ear. See Ear.