dinner jacket

So called because it is worn by men to formal dinners.

dinner jacket (plural dinner jackets)

1. (especially US) A jacket, often white, corresponding to a tuxedo jacket.
   • 1959, Kurt Vonnegut, The Sirens of Titan, New York: Dial, 2006, Chapter 2, p. 49,

     Constant was fully dressed in blue-green evening shorts and a dinner jacket of gold brocade.

   • 2012, Tan Twan Eng, The Garden of Evening Mists, Hachette, Chapter 10, p. 126,

     He was dressed in a gray dinner jacket and matching trousers.

2. (Britain) The formal suit, typically black, that includes this type of jacket.

   Synonyms: black tie, penguin suit

   • 1932, Nevil Shute, Lonely Road, Chapter 2,

     [They] sat in a pen in the corner, smoking cigarettes and reading magazines; four or five girls in black silk dresses and the same number of slight effeminate young men in dinner-jackets.

   • 1934, George Orwell, Burmese Days, Chapter 17,

     Mr Lackersteen was even wearing a dinner-jacket—white, because of the season—and was completely sober. The boiled shirt and piqué waistcoat seemed to hold him upright and stiffen his moral fibre like a breastplate.

   • 1971, E. M. Forster, Maurice, Penguin, 1972, Chapter 37, p. 162,

     It was a dinner-jacket evening—not tails, because they would only be three—and though he had respected such niceties for years he found them suddenly ridiculous.