From Longman Dictionary of Contemporary Englishstag partyˈstag ˌparty noun [countable] PARTYMARRYa party for men only, especially on a night before a man’s wedding → hen party
Examples from the Corpus
stag party• This is supposed to be a stag party, not an annual general meeting.• The first thing to take into account when planning a stag party is group mentality.• Of the stag party now only Jack, Charlie, George and one other remained. 