Available Definitions:
1) n. - One of the small divisions of a decompound frond or leaf. See Illust . of Bipinnate leaf, under Bipinnate.
2) n. - Any one of a series of small, slender organs, or parts, when arranged in rows so as to have a plumelike appearance; as, a pinnule of a gorgonia; the pinnules of a crinoid.