When a guy spanks or slaps another person with
semen on his
hand - i.e. just after masturbating.
This is a generally condescending move on par with tea-bagging, and - if executed properly - causes considerable distress on the recipient's end. Do not attempt this on someone that is physically stronger than you because they
will perceive it as a sign of great disrespect.
"John was being a
real douche last night, so I jerked it to a picture of his
girlfriend and then spunked him in his sleep."
"Dude, knock it off or I'll spunk you."