tail fin

noun
  1. 1

    A fin at the tail of a fish, caudal fin

  2. 2

    A fin on the tail of an aircraft, vertical stabilizer

  3. 3

    A fin-like projection at the rear of a car, common on American cars of the 1950s.

Source: https://en.wiktionary.org/wiki/tail%20fin, https://en.wiktionary.org/wiki/tailfin