Definition of "black-tie" [black-tie]

• Moderately formal; usually requiring a dinner jacket (tuxedo) for men. (adjective)

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• "That evening I was attending a big Democratic Party dinner at the Shoreham Hotel in Washington, a black-tie fund-raiser, and the news spread through the room with whispers and gasps."
• "The Awards were announced at a black-tie event here in New York with the Indian Ambassador to the U.S., the Hon."
• "I used to quite enjoy going to the black-tie Balls at Uni in Scotland, but the idea of office get-togethers here in north america fills me with horror."