Definition of "straight man"

straight man

noun
plural straight men
1. (idiomatic) A member (of any gender) of a team of comic performers who plays a supporting role by helping to set up jokes and punch lines through engaging in dialog with another comedian playing a more eccentric or otherwise more interesting character; a foil who plays such a role in theatrical comedy.
  Quotations
  Recently he had successfully concluded a case featuring a poet who wore only latex, lived on liquorice allsorts and worshipped a horse she believed to be the reincarnation of Radclyffe Hall. And she was the straight man.
  2010, Caroline Graham, A Ghost in the Machine, Hachette UK
  She was the straight man, he was the comedian, and their audience was “standing room only” when they stepped up to the microphone.
  1982 April, Pam Hait, “Sandra Day O’Connor: Warm, Witty and Wise”, in The Ladies' Home Journal, volume 99, page 46
2. Used other than figuratively or idiomatically: see straight,‎ man; for example, a heterosexual man.