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1.
Effeleven/F11 - refers to a night out on which the date is Friday 11th - this happens a few times a year and is a celebration outright hedonism. This night is often subject to debauchery on a biblical scale.

An F11 may ocour when a select group of friends execute a night out of unheard proportions. The type of night out where stories will be told, heroes made and benchmarks for a generation set.

Besides mass amounts alcohol, there is often gambling, strippers and sheer disregard for personal safety associated with an F11 night.

The build up to an F11 can take months.
A: I cannot wait for this night out, it is going to be completely savage..
B: Yeah, we are going to Effeleven that shit.

A: What the fuck happened last night? I've woken up with 2 hookers, a dead dog and I have a tattoo on my dick..
B: Don't know mate - we fucking Effelevned it.

A: Did you hear about those guys? They blew 10k in one night out, I heard one of them actually had a heart attack..
B: That's so Effeleven.
by thejmlevmeister November 09, 2011