fin

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noun (1)

ˈfin 

1

: an external membranous process of an aquatic animal (such as a fish) used in propelling or guiding the body see fish illustration

2

: something resembling a fin: such as

a

: hand, arm

b(1)

: an appendage of a boat (such as a submarine)

(2)

: an airfoil attached to an airplane for directional stability

c

: flipper sense 1b

d

: any of the projecting ribs on a radiator or an engine cylinder

finlike

ˈfin-ˌlīk 

adjective

fin

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verb

finned; finning

transitive verb

: to equip with fins

intransitive verb

1

: to show the fins above the water

2

: to move through water propelled by fins

fin

3 of 4

noun (2)

slang

: a 5-dollar bill

fin

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abbreviation

1

finance; financial

2

finish

Examples of fin in a Sentence

Recent Examples on the Web

Noun

The new species was identified by its DNA, bone structure, body proportions, fin shape, head shape, coloring and other subtle physical features, the study said. —Aspen Pflughoeft, Miami Herald, 9 Sep. 2025

Beyond battery optimization, the fins are also designed for biomimetic performance enhancement. —New Atlas, 8 Sep. 2025

Verb

Using advanced imaging techniques, an international research team has reconstructed an ancient extinct fish’s heart, brain, and fins from an intricately detailed, fingernail-sized fossil fragment. —Andrew Paul, Popular Science, 6 Aug. 2025

Dogfish, a smaller fish, are fished commercially for their meat and are less likely to be discarded after finning. —Kaitlin McCallum, Hartford Courant, 17 May 2025

Word History

Etymology

Noun (1)

Middle English finn, from Old English

Noun (2)

Yiddish finf five, from Middle High German, from Old High German — more at five

First Known Use

Noun (1)

before the 12th century, in the meaning defined at sense 1

Verb

1933, in the meaning defined at transitive sense

Noun (2)

1916, in the meaning defined above

Phrases Containing fin

• dorsal fin
• fin de siècle
• fin whale
• lobe-fin
• pectoral fin
• pelvic fin
• swim fin
• tail fin

Rhymes for fin

• been
• bin
• chin
• din
• djinn
• finn
• gin
• grin
• in
• kin
• linn
• linne

Kids Definition

fin

noun

ˈfin

1

: a thin process on the outside of an aquatic animal (as a fish or whale) used in propelling or guiding the body

2

: something shaped like a fin

finlike

-ˌlīk

adjective

finned

ˈfind

adjective