Pin'na, n.

n. [Lat. pinna, penna, feather.]

1. (Bot.) One leaflet of a pinnate leaf, or branch of a compound pinnate leaf. Henslow.
2. [Lat. pinna, Gr. πίννα.] (Zoöl.) A mollusk of great size, having two equal valves closely united by a ligament along one of the sides. The byssus of several species of pinna is as fine and brilliant as silk, and has been used in manufacturing precious stuffs. It anchors itself to the rocks by its byssus. Cuvier.