A "Bourne Night" is the Act of Consuming a level of alcahol that results in memory loss to the Extent that very little or nothing can be Remembered of the Drunk Period once sober. The name is derived from the popular Bourne films in which the protagonist has no memory of certain events.
Dean: "I cant belive you tried to drink toilet water last night man!"
Tyler: "Really? I cant remember"
Dean: "Bourne Night, Yeah?"