- See under swallowtail(def 2).
- the tail of a swallow or a deeply forked tail like that of a swallow.
- any of several butterflies of the genus Papilio, characterized by elongated hind wings that resemble the tail of a swallow, as P. polyxenes (black swallowtail).Compare spicebush swallowtail, tiger swallowtail, zebra swallowtail.
- tail coat.
- any of various butterflies of the genus Papilio and related genera, esp P. machaon of Europe, having a tail-like extension of each hind wing: family Papilionidae
- the forked tail of a swallow or similar bird
- short for swallow-tailed coat