fin

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. 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.
2. n. Something resembling a fin in shape or function, as:
3. n. A fixed or movable airfoil used to stabilize an aircraft, missile, or projectile in flight.
4. n. A thin, usually curved projection attached to the rear bottom of a surfboard for stability.
5. n. A projecting vane used for cooling, as on a radiator or an engine cylinder.
6. n. See tail fin.
7. n. See flipper.
8. v. To equip with fins.
9. v. To emerge with the fins above water.
10. v. To swim, as a fish.
11. v. To lash the water with the fins. Used of a dying whale.
12. n. Slang A five-dollar bill.

Century Dictionary and Cyclopedia

1. n. 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. In fishes there are unpaired or vertical and paired or horizontal fins. The former are dorsal, anal, or caudal. The paired fins are pectoral and ventral, the former homologous with the anterior member or manus (hand) of terrestrial vertebrates, the latter homologous with the posterior member or pes (foot). The relations of the spinous and soft portions of the dorsal and anal fins, and the position and structure of the ventral fins, as well as various other modifications of all the fins, have been much utilized for the classification and discrimination of groups in ichthyology. The names of the fins are commonly abbreviated A., C., D., P., V., as in the accompanying figure. In the lower fishes the fins are sustained in an erect position by numerous filamentary or slender rods (actinotrichia), but in the typical fishes there is a growing together of the actinotrichia into special rays or spines. In various forms (Nematognathi, Salmonidæ, etc.) there is likewise a pocket-like sac or ridge on the hinder part of the back, generally consisting of adipose matter and called an adipose fin.
2. n. In sporting, a general term for fish, as in the phrase “fin, fur, and feather.”
3. n. Something resembling a fin.
4. n. A fin-like organ or attachment, or one appearing or used like a fin; in slang language, the hand.
5. n. The sharp plate in the colter of a plow.
6. n. 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.
7. n. In com., a blade of whalebone.
8. n. 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.
9. n. A tongue on the edge of a board.
10. n. See the adjectives, and def. 1.
11. To carve or cut up, as a fish.
12. To fin out: as, a finning whale.
13. n. A Middle English form of fine.
14. A Middle English form of fine.
15. A dialectal variant of find.
16. n. See Finn.
17. n. The thin sheet of metal squeezed out between the collars of the rolls in a roll-train.
18. n. An abbreviation of the Latin ad finem, at or to the end.
19. n. An abbreviation of Finland;
20. n. of Finnish.

Wiktionary

1. n. ichthyology One of the appendages of a fish, used to propel itself and to manoeuvre/maneuver.
2. n. A similar appendage of a cetacean or other marine animal.
3. n. A thin, rigid component of an aircraft, extending from the fuselage and used to stabilise and steer the aircraft.
4. n. A similar structure on the tail of a bomb, used to help keep it on course.
5. n. A hairstyle, resembling the fin of a fish, in which the hair is combed and set into a vertical ridge along the top of the head from about the crown to the forehead.
6. n. A device worn by divers and swimmers on their feet.
7. n. An extending part on a surface of a radiator, engine, heatsink, etc., used to facilitate cooling.
8. n. A sharp raised edge (generally in concrete) capable of damaging a roof membrane or vapor retarder.
9. v. transitive To cut the fins from a fish, shark etc
10. v. intransitive To swim in the manner of a fish
11. v. transitive To provide (a motor vehicle etc) with fins
12. n. US, slang A five-dollar bill.

GNU Webster's 1913

1. v. To carve or cut up, as a chub.
2. n. obsolete End; conclusion; object.
3. n. (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.
4. n. (Zoöl.) A membranous, finlike, swimming organ, as in pteropod and heteropod mollusks.
5. n. Slang, engraving, Slang, engraving A finlike organ or attachment; a part of an object or product which protrudes like a fin.
6. n. Slang, engraving, engraving The hand.
7. n. (Com.), engraving A blade of whalebone.
8. n. (Mech.) A mark or ridge left on a casting at the junction of the parts of a mold.
9. n. (Mech.) The thin sheet of metal squeezed out between the collars of the rolls in the process of rolling.
10. n. (Mech.) A feather; a spline.
11. n. A finlike appendage, as to submarine boats.
12. n. (Aëronautics) A fixed stabilizing surface, usually vertical, similar in purpose to a bilge keel on a ship.

WordNet 3.0

1. n. one of a pair of decorations projecting above the rear fenders of an automobile
2. n. organ of locomotion and balance in fishes and some other aquatic animals
3. v. show the fins above the water while swimming
4. n. a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
5. n. a stabilizer on a ship that resembles the fin of a fish
6. n. one of a set of parallel slats in a door or window to admit air and reject rain
7. v. propel oneself through the water in a finning motion
8. n. the cardinal number that is the sum of four and one
9. v. equip (a car) with fins