Jump to:

• fin
  fin

  noun

  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.
• fin.
  fin.

  abbreviation

  finance.
• Fin.
  Fin.

  abbreviation

  Finland.
• FIN
  FIN

  abbreviation

  Finland (international car registration)
• Fin
  Fin

  abbreviation

  Finland

fin

¹ American  

[fin] / fɪn /

noun

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.

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.

---

verb (used with object)

finned, finning

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, finning

1. to move the fins; lash the water with the fins, as a whale when dying.

fin ² American  

[fin] / fɪn /

noun

1. Slang. a five-dollar bill.

---

fin. ³ American  

abbreviation

1. finance.

2. financial.

3. finish.

---

Fin. ⁴ American  

abbreviation

1. Finland.

2. Finnish.

---

FIN ¹ British  

abbreviation

1. Finland (international car registration)

---

fin ² British  

/ fɪn /

noun

1. slang a five-dollar bill

---

fin ³ British  

/ fɪn /

noun

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. 1. 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

   2. 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

---

verb

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

Fin ⁴ British  

abbreviation

1. Finland

2. Finnish

---

fin. ⁵ British  

abbreviation

1. finance

2. financial

---

fin Scientific  

/ fĭn /

1. One of the winglike or paddlelike parts of a fish, dolphin, or whale that are used for propelling, steering, and balancing in water.

---

Other Word Forms

• finless
  adjective
• finlike
  adjective

Etymology

Origin of fin¹

First recorded before 1000; Middle English, Old English finn; cognate with Dutch vin, Low German finne; akin to Swedish fena; probably akin to Latin pinna ( def. ); see also pen ¹ ( def. )

Origin of fin²

First recorded in 1865–70; earlier finnip, finnup, fin(n)if “a five-pound note,” from Yiddish fin(e)f “five,” from Middle High German vumf, vimf; see origin at five

Explanation

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."

Example Sentences

His father, Chris Sullivan, 65, told BBC London he had lost his only son, who was referred to by friends and family as Fin.

From BBC • Apr. 12, 2026

Fin Smith was fortunate that Lorenzo Cannone's charge-down of his 13th-minute kick did not result in a try for Italy.

From BBC • Mar. 12, 2026

Fly-half Fin Smith and inside centre Seb Atkinson came up through the Worcester youth system and featured in six first-team games together half a decade ago.

From BBC • Mar. 6, 2026

At age 92, his first opera "Fin de partie" premiered at Milan's famous La Scala in late 2018.

From Barron's • Feb. 18, 2026

Fin was seated on a stool at her workbench, mending a gardening tool.

From "Huntress" by Malinda Lo