fin

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A five-dollar bill.
• noun A membranous appendage extending from the body of a fish or other aquatic animal, used for propelling, steering, or balancing the body in the water.
• noun Something resembling a fin in shape or function, as.
• noun A covering for the foot having a flat flexible portion made of rubber or plastic that widens as it extends forward from the toes, used to provide enhanced propulsion in swimming and diving.
• noun A fixed or movable airfoil used to stabilize an aircraft, missile, or projectile in flight.
• noun A thin, usually curved projection attached to the rear bottom of a surfboard for stability.
• noun A projecting vane used for cooling, as on a radiator or an engine cylinder.
• intransitive verb To equip with fins.
• intransitive verb To emerge with the fins above water.
• intransitive verb To swim, as a fish.
• intransitive verb To lash the water with the fins. Used of a dying whale.

from The Century Dictionary.

• To carve or cut up, as a fish.
• To fin out: as, a finning whale.
• A Middle English form of fine.
• A dialectal variant of find.
• noun See Finn.
• noun The thin sheet of metal squeezed out between the collars of the rolls in a roll-train.
• noun An abbreviation of the Latin ad finem, at or to the end.
• noun An abbreviation of Finland;
• noun of Finnish.
• noun A Middle English form of fine.
• noun An extension from the body of an aquatic animal, which serves for propelling, steering, or balancing in the water, and is developed from various parts of the body, generally as an alate or wing-like organ; a pinna.
• noun In sporting, a general term for fish, as in the phrase “fin, fur, and feather.”
• noun Something resembling a fin.
• noun A fin-like organ or attachment, or one appearing or used like a fin; in slang language, the hand.
• noun The sharp plate in the colter of a plow.
• noun In molding, a thin projection on the surface of a casting, caused by the imperfect approximation of two molding-boxes, containing each a part of the mold. The fin is formed by the metal running in between the two parting surfaces.
• noun In com., a blade of whalebone.
• noun A slip inserted longitudinally into a shaft or arbor, and left projecting so as to form a guide for an object which may slip upon it, but not rotate.
• noun A tongue on the edge of a board.
• noun See the adjectives, and def. 1.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To carve or cut up, as a chub.
• noun obsolete End; conclusion; object.
• noun (Zoöl.) 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.
• noun (Zoöl.) A membranous, finlike, swimming organ, as in pteropod and heteropod mollusks.
• noun Slang, engraving, Slang, engraving A finlike organ or attachment; a part of an object or product which protrudes like a fin.
• noun Slang, engraving, engraving The hand.
• noun (Com.), engraving A blade of whalebone.
• noun (Mech.) A mark or ridge left on a casting at the junction of the parts of a mold.
• noun (Mech.) The thin sheet of metal squeezed out between the collars of the rolls in the process of rolling.
• noun (Mech.) A feather; a spline.
• noun A finlike appendage, as to submarine boats.
• noun (Aëronautics) A fixed stabilizing surface, usually vertical, similar in purpose to a bilge keel on a ship.
• noun (Zoöl.) See under Adipose, a.
• noun (Anat.) one of the hornlike, cartilaginous, or bony, dermal rods which form the skeleton of the fins of fishes.
• noun (Zoöl.) a finback.
• noun (Zoöl.) the pectoral and ventral fins, corresponding to the fore and hind legs of the higher animals.
• noun (Zoöl.) the dorsal, caudal, and anal fins.