✈️ A plane's rear fin 🚗 A car's rear fin

tailfin

1 6.5

A pointed upright part at the back of some cars popular in the 1950s

noun
/ˈteɪlˌfɪn/

Archaic

: aleta trasera

Many car enthusiasts appreciate the unique shapes of tailfins that were popular in mid-century automobile designs.
Cadillac tailfins

Examples

Classic cars from the 1950s often featured elegant tailfins that added a stylish touch to their design.
The bright chrome tailfins on the vintage Cadillac gleamed under the sun, attracting many admirers.
Nearly everything is optional, you see, from the trim on the tailfins to the color of the seatbelts.

Blog text (25)
Here and there sparkled the artificial colors of mid-fifties Cadillac tailfins.

Fiction book (1994)

Synonyms

fin

vstailfin

Archaic

9 7.3

A decorative metal piece on the back of some old cars

is a single thin vertical projection extending past the rear fenders

tail fin

vstailfin

Archaic

1 6.4

A decorative metal piece on a car's rear that looks like a small wing

is thinner and vertical and extends clearly beyond the rear fenders

How Prominent

tailfin

Archaic

1 6.5

fin

Archaic

9 7.3

Surface Forms

tailfin singular

tailfins plural

Morphology

tailfin = tail + fin (transparent) = tail + fin

A straightforward compound: 'tail' (rear) + 'fin' (projecting feature); decorative car fins extend above the rear and the compound meaning is inferable.

Etymology

Tailfin comes from the parts tail and fin, where tail means 'the back part' and fin means 'a flat part like a fish fin'. Car tailfins were small fins added to the back of cars as a decorative feature, copied from airplane and jet designs to make cars look modern in the 1950s.