To drink; to get wasted. [Silly] is another term for drunk.
> Your kid: "Hey guys, I stole a 12-pack of [Natty] from my dad's fridge. Wanna get silly tonight."
> Friend: "No, I think we'll just smoke crack instead."
> Your kid: "OK, save a couple rocks for me!"
> "Get silly...don't stop when the beat drop, just keep shakin' it, get silly." -Sean Paul
> "Got me gettin' so silly right now..." -Beyonce
> "E'rybody in the club gettin' silly." -J-Kwon