The Collaborative International Dictionary of English v.0.48:
Fin \Fin\, n.[OE. finne, fin, AS. finn; akin to D. vin, G. &
Dan. finne, Sw. fena, L. pinna, penna, a wing, feather. Cf.
pen a feather.]
1. (Zool.) An organ of a fish, consisting of a membrane
supported by rays, or little bony or cartilaginous
ossicles, and serving to balance and propel it in the
Note: Fishes move through the water chiefly by means of the
caudal fin or tail, the principal office of the other
fins being to balance or direct the body, though they
are also, to a certain extent, employed in producing
2. (Zool.) A membranous, finlike, swimming organ, as in
pteropod and heteropod mollusks.
3. A finlike organ or attachment; a part of an object or
product which protrudes like a fin, as:
(a) The hand. [Slang]
(b) (Com.) A blade of whalebone. [Eng.] --McElrath.
(c) (Mech.) A mark or ridge left on a casting at the
junction of the parts of a mold.
(d) (Mech.) The thin sheet of metal squeezed out between
the collars of the rolls in the process of rolling.
(e) (Mech.) A feather; a spline.
4. A finlike appendage, as to submarine boats.
5. (A["e]ronautics) A fixed stabilizing surface, usually
vertical, similar in purpose to a bilge keel on a ship.
[Webster 1913 Suppl.]
Apidose fin. (Zool.) See under Adipose, a.
Fin ray (Anat.), one of the hornlike, cartilaginous, or
bony, dermal rods which form the skeleton of the fins of
Fin whale (Zool.), a finback.
Paired fins (Zool.), the pectoral and ventral fins,
corresponding to the fore and hind legs of the higher
Unpaired fins, or Median fins (Zool.), the dorsal,
caudal, and anal fins.