tailcoat
/ˈteɪlˌkoʊt/
noun
- A formal coat with a long back split into two tails, typically worn by men as part of white-tie or evening dress.
- At the gala, all the men in the orchestra wore tailcoats.
- He rented a tailcoat for the formal dinner dance.
- The groom wore a black tailcoat and white bow tie for the wedding.