noun, verb, finned, fin⋅ning.| 1. | a membranous, winglike or paddlelike organ attached to any of various parts of the body of fishes and certain other aquatic animals, used for propulsion, steering, or balancing. |
| 2. | Nautical.
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| 3. | Also called vertical stabilizer. Aeronautics. any of certain small, subsidiary structures on an aircraft, designed to increase directional stability. |
| 4. | any of a number of standing ridges on an ordinarily hot object, as a radiator, a cylinder of an internal-combustion engine, etc., intended to maximize heat transfer to the surrounding air by exposing a large surface area. |
| 5. | any part, as of a mechanism, resembling a fin. |
| 6. | Metallurgy. a ridge of metal squeezed through the opening between two rolls, dies, or halves of a mold in which a piece is being formed under pressure. Compare flash (def. 11). |
| 7. | Automotive. an ornamental structure resembling an aeronautical fin that is attached to the body of an automobile, as on each rear fender (tail fin). |
| 8. | Slang. the arm or hand. |
| 9. | Usually, fins. flipper (def. 2). |
| 10. | to cut off the fins from (a fish); carve or cut up, as a chub. |
| 11. | to provide or equip with a fin or fins. |
| 12. | to move the fins; lash the water with the fins, as a whale when dying. |

fin 1 (fĭn) n.
v. tr. To equip with fins. v. intr.
[Middle English, from Old English finn.] |
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fin
[fɪn] and finn
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