noun
also pin·ule ˈpin(ˌ)yül
( -s )
Etymology: New Latin pinnula, from Latin, small feather, small fin
1. : a small plate (as in an alidade) pierced with a peephole
2.
a. : one of the secondary branches of a plumelike organ ; specifically : one of the lateral parts of the arm of a crinoid or of the tentacle of an alcyonarian polyp
b. : a small detached fish fin (as behind the dorsal and anal fins of the mackerel) : finlet
3. : a secondary pinna : one of the ultimate divisions of a bipinnate or twice-pinnate leaf