Definition of "swallowtail" []

• The deeply forked tail of a swallow. (noun)
• Something similar to the tail of a swallow. (noun)
• See tailcoat. (noun)
• Any of various colorful, widely distributed butterflies of the family Papilionidae, usually having an extension at the end of each hind wing that resembles the tails of certain swallows. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "It was of a style popularly known as a swallowtail, faced with satin as to lapels and once gracefully rounded to a long, bisected skirt in the rear."
• "Informal evening dress differs from formal in the wearing of the Tuxedo or dinner coat in place of the "swallowtail," and the substitution of a black silk for a white lawn tie."
• "He was punctiliously dressed in the mode: a "swallowtail," bright, soft silk tie of ample proportions, frilled linen, and sparkling studs."