stag

A groom's outing with his male friends before his wedding; a bachelor party. Mark knew that his stag night had gotten out of control when the police arrived.

A groom's outing with his male friends before his wedding; a bachelor party. Mark knew that his stag party had gotten out of control when the police arrived.

to go to an event (which is meant for couples) without a member of the opposite sex. (Originally referred only to males.) Is Tom going to take you, or are you going stag? Bob didn't want to go stag, so he took his sister to the party.

a party for a man who is going to get married, to which only his male friends are invited On Keith's stag night, his friends left him tied to a lamp-post in Trafalgar Square, wearing only his underpants.

if a man goes stag to a social event, he goes without a woman He usually prefers to go stag to parties.

Go unaccompanied by a person of the opposite sex to a social event, as in John decided to go stag to his roommate's party, or Some of the girls are going stag to the dance. Although this term originally applied only to men attending an event without a woman companion, it is now applied to women as well. [c. 1900]

A social gathering for men exclusively, often involving entertainment considered unsuitable for women. For example, They wanted to give him a stag party before the wedding but John wasn't interested. This idiom uses stag in the sense of "a man unaccompanied by a woman." [c. 1850]

Unattached men at a dance. Men who had no date for a dance but still wanted to go would stand along one wall and either ask unattached women to dance or cut in on a couple that was dancing. Going stag to a dance had no unpleasant connotation. Not so for unattached females, known as “wallflowers.” True or not, wallflowers were suspected of not being popular enough to attract a date.