Unpaired fins

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. (Zo["o]l.) 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 water. [1913 Webster]

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 motion. [1913 Webster]

2. (Zo["o]l.) A membranous, finlike, swimming organ, as in pteropod and heteropod mollusks. [1913 Webster]

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. --Raymond. (e) (Mech.) A feather; a spline. [1913 Webster]

4. A finlike appendage, as to submarine boats. [1913 Webster]

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}. (Zo["o]l.) See under {Adipose}, a.

{Fin ray} (Anat.), one of the hornlike, cartilaginous, or bony, dermal rods which form the skeleton of the fins of fishes.

{Fin whale} (Zo["o]l.), a finback.

{Paired fins} (Zo["o]l.), the pectoral and ventral fins, corresponding to the fore and hind legs of the higher animals.

{Unpaired fins}, or {Median fins} (Zo["o]l.), the dorsal, caudal, and anal fins. [1913 Webster]