See more synonyms for fin on
  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.
    1. 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.
    2. fin keel.
  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).
verb (used with object), finned, fin·ning.
  1. to cut off the fins from (a fish); carve or cut up, as a chub.
  2. to provide or equip with a fin or fins.
verb (used without object), finned, fin·ning.
  1. to move the fins; lash the water with the fins, as a whale when dying.

Origin of fin

before 1000; Middle English, Old English finn; cognate with Dutch vin, Low German finne; akin to Swedish fena
Related formsfin·less, adjectivefin·like, adjective


  1. Slang. a five-dollar bill.

Origin of fin

1865–70; earlier finnip, finnup, fin(n)if(f) a five-pound note < Yiddish fin(e)f five < Middle High German vumf, vimf; see five



ad fin.

  1. to, toward, or at the end.

Origin of ad fin.

ad fīnem Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for fin

hand, vane, appendage, pinna, stabilizer, flipper, airfoil, dorsal

Examples from the Web for fin

Contemporary Examples of fin

Historical Examples of fin

British Dictionary definitions for fin


  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
    1. Britisha vertical surface to which the rudder is attached, usually placed at the rear of an aeroplane to give stability about the vertical axisUS name: vertical stabilizer
    2. a tail surface fixed to a rocket or missile to give stability
  3. nautical a fixed or adjustable blade projecting under water from the hull of a vessel to give it stability or control
  4. a projecting rib to dissipate heat from the surface of an engine cylinder, motor casing, or radiator
  5. (often plural) another name for flipper (def. 2)
verb fins, finning or finned
  1. (tr) to provide with fins
  2. (tr) to remove the fins from (a dead fish)
  3. (intr) (esp of a whale) to agitate the fins violently in the water
Derived Formsfinless, adjective

Word Origin for fin

Old English finn; related to Middle Dutch vinne, Old Swedish fina, Latin pinna wing


  1. US slang a five-dollar bill

Word Origin for fin

from Yiddish finf five, ultimately from Old High German funf, finf


abbreviation for
  1. Finland
  2. Finnish


abbreviation for
  1. Finland (international car registration)


abbreviation for
  1. finance
  2. financial
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for fin

Old English finn, from Proto-Germanic *finno (cf. Middle Low German vinne, Dutch vin), perhaps from Latin pinna "feather, wing" (see pin (n.)); or, less likely, from Latin spina "thorn, spine" (see spike (n.1)).

U.S. underworld slang sense of "$5 bill" is 1925, from Yiddish finif "five," from German fünf (see five) and thus unrelated. The same word had been used in England 1868 to mean "five pound note" (earlier finnip, 1839).

Online Etymology Dictionary, © 2010 Douglas Harper

fin in Science


  1. 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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.