'black-tie' definitions:

Definition of 'black-tie'

From: WordNet
adjective
Moderately formal; requiring a dinner jacket; "he wore semiformal attire"; "a black-tie dinner" [syn: semiformal, semi-formal, black-tie]

Definition of 'black-tie'

From: GCIDE
  • black-tie \black-tie\ adj. requiring semiformal evening clothes, e. g. a black bowtie and a tuxedo or dinner jacket for men, and a formal dress for women; contrasted with white-tie, for a fully formal occasion, and with informal, and casual. a black-tie dinner
  • Syn: semi-formal, semiformal. [WordNet 1.5 +PJC]