Definition from Wiktionary, the free dictionary
swallowtail (plural swallowtails)
- The forked tail of a swallow.
- Anything, such as a burgee, of a similar forked shape.
- A type of tailcoat with two long tapering tails.Wp
- Any of various butterflies of the family Papilionidae, having a forked extension to the hind wing.
tail of a swallow