- n a stabilizer that is part of the vertical tail structure of an airplane
- n one of a pair of decorations projecting above the rear fenders of an automobile
- Loewy's own car had a few special flamboyant frills: a plastic tailfin, a tiny gold grilled air scoop above the emblem on the hood, recessed door handles, porthole windows and .
- Testing his controls with a wide, lazy-S turn, Crossfield, following procedure, jettisoned the X-15's ventral tailfin, which would have interfered with extending his tail .
- Grammarwise, it is permissible to tailfin any word with the suffix meaning "in the manner of.