A Slice head is an emo / depressed / insane person whom is addicted to cutting themselves. Calling someone a slice head is like calling them stupid or crazy.
(Literal use) Did you see those cuts on Isaacs arms? He's obviously a slice head
(Insult use) Logan: Hey dude did you see the emoji movie? It was sick.
I didn't imagine that I'd have any problem getting to the game on time but I got stuck behind a couple of silverheads and missed most of the first quarter.
When a girl takes a shit in her own hand and then she gets on her knees, eats your asshole out from behind while the male is standing up and she also jerks you off at the same time with her shit filled hand.