1.NounA 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.
"For many years Bud Abbott served brilliantly as Lou Costello's deadpan straight man."
2.NounUsed other than figuratively or idiomatically: see straight, man; for example, a heterosexual man.
"The committee consisted of two lesbians and a straight man."