tail fin

definition: the tail of fishes and some other aquatic vertebrates
example:
speech part: noun
synonyms: caudal fin
definition: one of a pair of decorations projecting above the rear fenders of an automobile
example:
speech part: noun
synonyms: fin
definition: a stabilizer that is part of the vertical tail structure of an airplane
example:
speech part: noun
synonyms: tailfin vertical stabilizer vertical fin

How tail fin is being used?