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1 [fin]
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.
a horizontal, often adjustable, winglike appendage to the underwater portion of a hull, as one for controlling the dive of a submarine or for damping the roll of a surface vessel.
Also called vertical stabilizer. Aeronautics. any of certain small, subsidiary structures on an aircraft, designed to increase directional stability.
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.
any part, as of a mechanism, resembling a fin.
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 ).
Automotive. an ornamental structure resembling an aeronautical fin that is attached to the body of an automobile, as on each rear fender (tail fin)
Slang. the arm or hand.
Usually, fins. flipper ( def 2 ).
verb (used with object), finned, finning.
to cut off the fins from (a fish); carve or cut up, as a chub.
to provide or equip with a fin or fins.
verb (used without object), finned, finning.
to move the fins; lash the water with the fins, as a whale when dying.

before 1000; Middle English, Old English finn; cognate with Dutch vin, Low German finne; akin to Swedish fena

finless, adjective
finlike, adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
fin1 (fɪn)
1.  any of the firm appendages that are the organs of locomotion and balance in fishes and some other aquatic animals. Most fishes have paired and unpaired fins, the former corresponding to the limbs of higher vertebrates
2.  a part or appendage that resembles a fin
3.  a.  (Brit) US name: vertical stabilizer a vertical surface to which the rudder is attached, usually placed at the rear of an aeroplane to give stability about the vertical axis
 b.  a tail surface fixed to a rocket or missile to give stability
4.  nautical a fixed or adjustable blade projecting under water from the hull of a vessel to give it stability or control
5.  a projecting rib to dissipate heat from the surface of an engine cylinder, motor casing, or radiator
6.  (often plural) another name for flipper
vb , fins, finning, finned
7.  (tr) to provide with fins
8.  (tr) to remove the fins from (a dead fish)
9.  (intr) (esp of a whale) to agitate the fins violently in the water
[Old English finn; related to Middle Dutch vinne, Old Swedish fina, Latin pinna wing]

fin2 (fɪn)
slang (US) a five-dollar bill
[from Yiddish finf five, ultimately from Old High German funf, finf]

abbreviation for
1.  Finland
2.  Finnish

abbreviation for
Finland (international car registration)

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

O.E. fin, from P.Gmc. *finno (cf. M.L.G. vinne, Du. vin), perhaps from L. pinna "feather, wing," or, less likely, from L. spina "thorn, spine" (see spike (n.1)). U.S. underworld slang sense of " bill" is 1925, from Yiddish finif "five," from Ger. fünf. The same word
had been used in England 1868 to mean "five pound note" (earlier finnip, 1839).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
fin   (fĭn)  Pronunciation Key 
One of the winglike or paddlelike parts of a fish, dolphin, or whale that are used for propelling, steering, and balancing in water.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Abbreviations & Acronyms
Finland (international vehicle ID)
The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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