FIN - A TCP segment used to close a connection. Each side must send a FIN.

A civilian word for the vertical and horizontal stabilizers on aircraft and the rudder and diving planes on a submarine. Also a type of footware used by SCUBA divers used for manuvering underwater in a more efficient manner than human appendages alone.

A distinctive decorative feature of American automobiles of the 1950s. Fins ususally protrude upward like the fins of fish from the rear of the vehicle.

Also, slang for a five dollar bill.

In the UK the fin is a structure above the main hull of a submarine that serves mainly as a streamlined fairing around the masts and antennas. On top of the fin is the bridge which is only used when the submarine is surfaced. If the submarine has a conning tower, the structure is known as a fairwater. In the US the fin is known as the sail.

See sail for an ASCII diagram.

The terms conning tower, fairwater, and sail are often (incorrectly) used interchangeably.

Fin (?), v. t. [imp. & p. p. Finned (?); p. pr. & vb. n. Finning.] [Cf. Fin of a fish.]

To carve or cut up, as a chub.


© Webster 1913

Fin, n. [See Fine, n.]

End; conclusion; object. [Obs.] "She knew eke the fin of his intent." Chaucer.


© Webster 1913

Fin, n.[OE. finne, fin, AS. finn; akin to D. vin, G. & Dan. finne, Sw. fena, L. pinna, penna, a wing, feather. Cf. pen a feather.]

1. (Zoöl.)

An organ of a fish, consisting of a membrane supported by rays, or little bony or cartilaginous ossicles, and serving to balance and propel it in the water.

⇒ Fishes move through the water chiefly by means of the caudal fin or tail, the principal office of the other fins being to balance or direct the body, though they are also, to a certain extent, employed in producing motion.

2. (Zoöl.)

A membranous, finlike, swimming organ, as in pteropod and heteropod mollusks.


A finlike organ or attachment; a part of an object or product which protrudes like a fin, as:


The hand. [Slang]

(b) (Com.)

A blade of whalebone. [Eng.] McElrath.

(c) (Mech.)

A mark or ridge left on a casting at the junction of the parts of a mold.

(d) (Mech.)

The thin sheet of metal squeezed out between the collars of the rolls in the process of rolling. Raymond.

(e) (Mech.)

A feather; a spline.


A finlike appendage, as to submarine boats.

Apidose fin. (Zoöl.) See under Adipose, a. --
Fin ray (Anat.), one of the hornlike, cartilaginous, or bony, dermal rods which form the skeleton of the fins of fishes. --
Fin whale (Zoöl.), a finback. --
Paired fins (Zoöl.), the pectoral and ventral fins, corresponding to the fore and hind legs of the higher animals. --
Unpaired, or Median, fins (Zoöl.), the dorsal, caudal, and anal fins.


© Webster 1913

Fin, n. (Aëronautics)

A fixed stabilizing surface, usually vertical, similar in purpose to a bilge keel on a ship.


© Webster 1913

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