also black-tie
1.
A black tie event is a formal social event such as a party at which people wear formal clothes called evening dress.
...a black-tie dinner for former students.
ADJ : usu ADJ n
2.
If a man is dressed in black tie , he is wearing formal evening dress, which includes a dinner jacket or tuxedo and a bow tie.
Most of the guests will be wearing black tie.
N-UNCOUNT