Unkown, but typically can refer to a state of intoxication so drunk that you can't form sentences and start making up words. Then it can mean just about anything. Can be shortened to slized if also high.
Getting slizzard like a g6.
That drink got me so slizzard.
Yo, Mr. Gregory I got so slizzard off your test.
I slized your mom
You dude I got slizzard, and then also slized.