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.
while performing oral sex on a girl you begin to lick her and realize there is a white string and you end up pulling out her tampon with your mouth as if you were bobbin for an apple...
A humerous game derived from the age old tradition of Bobbing for Apples, however, some clever dick has replaced the apples with rather unsavoury objects resulting in a rather messy game.