What is "adipose fin"

Adipose \Ad"i*pose`\ (?; 277), a. [L. adeps, adipis, fat, grease.] Of or pertaining to animal fat; fatty.

Adipose fin (Zo["o]l.), a soft boneless fin.

Adipose tissue (Anat.), that form of animal tissue which forms or contains fat.

n. (context ichthyology English) A soft, fleshy fin found on the back of a fish behind the dorsal fin and just forward of the caudal fin.