morning coat 
noun British
A man’s formal coat with a long back section cut into tails which curves up to join the waist at the front.For, as every dedicated follower of fashion knows, at Britain's most elegant race meeting, no gentleman gets into the enclosure without wearing the obligatory morning coat and top hat....
- Being a true English gent, I lend her the warm and comforting embrace of my morning coat.
- Hill himself was sitting in a corner in his morning coat.