fin

A fin is the part of a fish's body that protrudes into the water and helps it balance and move in various directions. Sharks use their dorsal fins to stabilize their bodies as they propel through the water.

Fish, whales, dolphins, and other aquatic animals have fins on various parts of their bodies. Surfboards often have a rear fin that works in a similar way, helping to keep the board steady and aid in making turns. Ships, cars, and aircraft also have fins that assist with balance. In Old English, it was finn, which probably comes from the Latin pinna, "feather or wing."

Definitions of fin
  1. noun
    organ of locomotion and balance in fishes and some other aquatic animals
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    types:
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    dorsal fin
    unpaired median fin on the backs of fishes and some other aquatic vertebrates that help to maintain balance
    pectoral fin
    either of a pair of fins situated just behind the head in fishes that help control the direction of movement
    pelvic fin, ventral fin
    either of a pair of fins attached to the pelvic girdle in fishes that help control the direction of movement; correspond to hind limbs of a land vertebrate
    caudal fin, tail fin
    the tail of fishes and some other aquatic vertebrates
    heterocercal fin
    a tail fin with unequal lobes in which the vertebral column turns upward into the larger lobe as in sharks
    homocercal fin
    symmetrical tail fin extending beyond the end of the vertebral column as in most bony fishes
    type of:
    appendage, extremity, member
    an external body part that projects from the body
  2. noun
    a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
    synonyms: flipper
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    type of:
    shoe
    footwear shaped to fit the foot (below the ankle) with a flexible upper of leather or plastic and a sole and heel of heavier material
  3. noun
    a stabilizer on a ship that resembles the fin of a fish
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    types:
    vane
    a fin attached to the tail of an arrow, bomb or missile in order to stabilize or guide it
    type of:
    stabiliser, stabilizer
    a device for making something stable
  4. verb
    propel oneself through the water in a finning motion
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    type of:
    swim
    travel through water
  5. verb
    show the fins above the water while swimming
    “The sharks were finning near the surface”
    synonyms: break water
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    type of:
    swim
    travel through water
  6. verb
    equip (a car) with fins
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    type of:
    equip, fit, fit out, outfit
    provide with (something) usually for a specific purpose
  7. noun
    one of a set of parallel slats in a door or window to admit air and reject rain
    synonyms: louver, louvre
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    type of:
    slat, spline
    a thin strip (wood or metal)
  8. noun
    one of a pair of decorations projecting above the rear fenders of an automobile
    synonyms: tail fin, tailfin
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    type of:
    decoration, ornament, ornamentation
    something used to beautify
  9. noun
    the cardinal number that is the sum of four and one
    synonyms: 5, Little Phoebe, Phoebe, V, cinque, five, fivesome, pentad, quint, quintet, quintuplet
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    type of:
    digit, figure
    one of the elements that collectively form a system of numeration
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