1.NounThe most formal kind of eveningwear for men, consisting of an evening tailcoat, trousers with strips of braid down the side seams, white stiff-fronted shirt, white bow tie and waistcoat with or without sash.
2.NounA dress code specifying white tie for men and ball gown or evening dress for women, or, alternatively, full military dress or national costume.
"You are cordially invited to dinner with His Excellency the President. Dress: White Tie."