Same as someone who kisses ass. Someone who is a cockride attempts to gain favor of a person with higher authority in order to gain their trust for reasons of personal gain or to show off.
Person 1: "Hey I think we should have a game of CoD?"
Person 2: "I think that we should play BF3 instead."
Coderider: "I want to play CoD on Person1's team!"
"Dave doesn't let anyone in his shed except Trent, what a fuckin' cockride."
-"Yeah, Jacob doesn't let just anyone into his mini-bar, but he lets me."
-"You're such a cockride cunt."