Its when you ejaculate in a sock (preferably cotton) multiple time and you run up to someone who is sleeping or just walking in the street and Pimp Smack them in the face with it.
Guy1 : *walking normaly in the street*
Guy2: Runs up and hits him with a sock.
Guy1: DUDE! WTF IS ON MY FACE!?
Guy2: You just got... Slimy Socked.
YEAAAAAAAAAAAAAAAAAAAAAA
When a persons feet sweat so much that when they take off their shoes, it's soaked in sweat and the sock has started drooping off the foot. Term was most likely started in the locker rooms of schools.
Eww Eric, your have slimy socks.