A tailcoat is a type of formal jacket that is usually worn by men. It is named after its long back section or "tail" that extends below the waist. Full definition
As someone was bound to comment, that is going to cost a fortune in tailcoats. (independent.co.uk)
As tailcoats evolved rapidly among the wealthy during the Regency period, various styles of closure saw popularity, from fastenings at the top, the middle, or even hanging open. (en.wikipedia.org)
Black tux style wool tailcoat with standing collar decorated by a satin insert to match the satin lapel. (1stdibs.com)