The act of bobbing your headup and down (almost sleeping) during a boring safety brief that is being given by a pussy officer. This usually occurs right before you get libbo.
pete: Check out that guy.
tom: Which on?
pete: the guy bobbing for cock...must of had too many drinks last night.
When someone is sitting upright and keeps falling asleep. When their head bobs down and they jerk it back up, it looks like they're giving head. Bobbin for cock.