(v./adj.) To troll, be extremely arrogant, annoying, pessimistic, sarcastic, lame, or asinine. Can also describe sudden coolness or superiority.
Depending on the attitude of the person "snewd" is being used to describe, it can also reflect upon things in a positive light.
-"Johnny was being very snewd today in class, he stuck gum to a classmates hair then glued their hands together behind their back."
-"Whoa! He just pushed a girl out of the way of a speeding truck! That was totally snewd. Praise him."