The lineup for weekends of binge drinking, partying, drug consumption, etc. with close friends.
Generally, the rounds begin on Friday nights and continue consecutively with each night consisting of harder drinking/partying.
Although most people who have lives end their rounds on Sunday night, essentially the rounds do not end until a member of the group decides to rest.
Round 1 - Friday night
Round 2- Saturday night
And if you can handle it
Round 3- Sunday night (usually known as the "Final Round")
Also see 'The Round to End All Rounds'