A name in Britain for a night also known as "the single man's last night of freedom". A
big event in any man's life, the stag night is quite indicative of the British male
booze culture. It is
quietly sentimental yet raucously outrageous, and this makes the
bride very nervous about what illicit activities her future husband will partake in on the night.
Traditionally occurring the night before the groom gets married, but it can be any night in the few weeks before the ceremony (due to the fact the groom doesn't feel like getting out of bed the day after, let alone managing getting married). The groom and his closest friends (between 5 - 20 closest friends) go out on the razzle and hold a celebration involving lots of alcohol and strippers - sometimes the stripper is also a prostitute. Incidental violence is not unknown to happen.
The men drink, reminisce, drink, enquire as to whether the groom is absolutely sure about wanting to get married, drink perhaps play some games: a dirty little favourite like "Guess who is getting a blowjob from the Prostitute under the table" in which every man must keep a straight face, if anyone is correctly guessed getting a blowjob they lose (note: I find that repulsive personally). Then everybody drinks some more.
The night usually ends with the groom being humiliated - the most popular method being to strip him from the waist down, handcuff him to a lamppost, with only a traffic cone to preserve his modesty. Although there have been stories where the groom has awoken to find himself in the middle of a field 100 miles away from the church with no money to get back - but one has to wonder if the people who do that to anyone are really his friends.
Of course all of this depends on how sensible and mature the men are, and whether they're middle-class or working class, northerner or southerner, etc. The stag night has many variations I have just listed a few.
The female equivalent of the stag night, is the Hen Night which I know little about other then it involves lots and lots of oiled male strippers whom the women grope, they also drink a lot, and tell dirty stories about past shags.