tail coat

noun

1. a man’s fitted coat, cut away over the hips and descending in a pair of tapering skirts behind, usually black and worn as part of full evening dress.

noun

1. Also called: tails a man’s black coat having a horizontal cut over the hips and a tapering tail with a vertical slit up to the waist: worn as part of full evening dress
2. Also called: swallow-tailed coat another name for morning coat