grow a pair

this doubly sexist term not only attacks a man's supposed manliness, but leaves women, who were born without testicles, in the position of never measuring up to the culture's standards of bravery and derring-do, as embodied in men. It also implies that all people who identify as men must have male sex organs, which isn't true either. It is used mainly in drunken brawls and by people with small vocabularies. See also man up.