A word with many meanings, can be used as an insult due to it's origin's being a type of Lizard, or alternatively as a way of describing a party/ drinking session.
As an insult/ banter
"What are you, a sailor"
"You're a fucking sleen"
As an adjective
"So, Larry's party tonight in town, all in for a long one?"
"Yeah man, we're gonna get Sleened!"