formal evening dress for men (distinguished from black tie
a white bow tie for men, worn with formal evening dress.
white-tiePronunciation: (hwīt'tī', wīt'-), [key]
requiring that guests wear formal attire, esp. that men wear white bow ties with formal evening dress: a white-tie embassy reception.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.