Etymology From Middle English fin, from Old English finn, from Proto-Germanic *finnō, *finǭ (“dorsal fin”) (compare Dutch vin, German Finne, Swedish finne, fena), from Proto-Indo-European *(s)pīn- (“backbone, dorsal fin”) (compare Old Irish ind (“end, point”), Latin pinna (“feather, wing, fin”), Tocharian A spin (“hook”).
Biology, Ichthyology, Natural sciences, Zoology, Zootomy One of the appendages of a fish, used to propel itself and to manoeuvre/maneuver.
The fish's fins minimize water flow.
Then he commenced to talk, really talk. and inside of two flaps of a herring's fin he had me mesmerized, like Eben Holt's boy at the town hall show. He talked about the ills of humanity, and the glories of health and Nature and service and land knows what all.1913, Joseph C[rosby] Lincoln, chapter IV, in Mr. Pratt’s Patients, New York, N.Y.; London: D[aniel] Appleton and Company, →OCLC:
2
A similar appendage of a cetacean or other marine animal.
a dolphin's fin
3
A thin, rigid component of an aircraft, extending from the fuselage and used to stabilise and steer the aircraft.
The fin stabilises the plane in flight.
4
A similar structure protruding from a projectile, used to help keep it on course.
5
Hobbies, Lifestyle, Sports, Surfing A similar structure on the bottom of a surfboard, used to help steer it.
6
A hairstyle, resembling the fin of a fish, in which the hair is combed and set into a vertical ridge along the top of the head from about the crown to the forehead.
7
A device worn by divers and swimmers on their feet.
The divers wore fins to swim faster.
8
An extending part on a surface of a radiator, engine, heatsink, etc., used to facilitate cooling.
9
A sharp raised edge (generally in concrete) capable of damaging a roof membrane or vapor retarder.
Etymology From Middle English fin, from Old English finn, from Proto-Germanic *finnō, *finǭ (“dorsal fin”) (compare Dutch vin, German Finne, Swedish finne, fena), from Proto-Indo-European *(s)pīn- (“backbone, dorsal fin”) (compare Old Irish ind (“end, point”), Latin pinna (“feather, wing, fin”), Tocharian A spin (“hook”).
1
To cut the fins from a fish, shark, etc.
2
(Of a fish) to swim with the dorsal fin above the surface of the water.
When you spot him finning just under the surface, you move up quietly and present [...] bait, usually a squid.1983, The Fisherman Who Laughed, page 54:
3
To swim in the manner of a fish.
A neutrally buoyant diver does not need to fin to maintain depth.
4
To provide (a motor vehicle etc) with fins.
fin
noun
Etymology From Yiddish פֿינף (finf, “five”). Doublet of cinque, finnuf, five, pimp (“five”), ponzu, punch (“beverage”), and sengi (“currency”).
1
UK, Slang a five-pound (£5) note; the sum of five pounds.
Formerly Australia
2
US, Dated, Slang A five-dollar bill; the sum of five dollars.
fin
noun
Etymology From French fin (“end”). Doublet of fine and finis.