The age that an American citizen, having been able to enlist in the military, purchase tobacco, vote, and enter a strip
club for three years
already, can finally go and buy a can of
beer.
Guy 1: "Hey, I heard you're 21 today! Here's a
beer!"
Guy 2: *puffs cigarette, shouting over strip club
music* "Thanks,
dude. Now I'll finally know what being an adult feels like."