1. requiring white ties and tailcoats for men; - Example: "a white-tie occasion"
The Collaborative International Dictionary of English v.0.48:
White-tie \White-tie\, a.
requiring formal evening clothes, usually interpreted as a
white bow tie and a tailcoat for men, and a formal evening
dress for women; -- as, a white-tie reception at the embassy.
Contrasting with black-tie and informal.
WordNet (r) 3.0 (2006):
adj 1: requiring white ties and tailcoats for men; "a white-tie