A cock suck in its most basic form is for a
woman (or in some undesirable incidents, a man) to take a
penis (cock) into their mouths and suck it. There are many variables on this technique (see "
walrus" and more).
"This one
bitch was really
drunk and I carried her about all night. I was getting a bit sick of her and everyone fucked off leaving just the two of us. I laid her down on her knees and said 'You owe me this'. Some might say that was a form of
rape, but hell, what a fuckin cock suck"