What is "power hour"

n. A drinking game in which players are challenged to drink a specified large number of shots of alcoholic drink within one hour.

Power Hour or 21 for 21 is a drinking event where player(s) drink a specified number of alcohol shots within one hour. Variants include one shot of beer every minute for an hour or 10 shots within one hour. In the USA, a power hour event is often associated with a person's 21st birthday when they reach the legal drinking age.