21 for 21

21 for 21
 n.— «The tradition is “power hour,” or “21 for 21,” as it is known in some other places across the country: 21-year-olds go to a bar at midnight on their birthdays, flash newly legal identification and then try to down 21 shots in the hour or so before the bar closes, or as fast as possible.» —“Drinking Game Can Be a Deadly Rite of Passage” by Kate Zernike in Fargo, N.D. New York Times Mar. 12, 2005. (source: Double-Tongued Dictionary)