1. (Science: marine biology, zoology) 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.
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.
2. (Science: marine biology) 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: The hand.
4. A finlike appendage, as to submarine boats. Apidose fin.
5. (Science: anatomy) The dorsal, caudal, and anal fins.
Origin: oe. Finne, fin, as. Finn; akin to D. Vin, g. & dan. Finne, Sw. Fena, L. Pinna, penna, a wing, feather. Cf. Pen a feather.