when you get too carried away with slapping a person or persons.
It could just be that you went on a slapping spree (greatly encouraged by me by the way, they're fun!)
or that you got so pissed off with someone that you just physically couldn't stop slapping them.
see doodle happy and scissor happy
person #1: "awwww owwww look at my face, is it red?"
person #2: "yeh why?"
person #1: "my ex-girlfriend got slap happy"
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me: i feel like going on a slapping spree...anyone want to come and get slap happy with me?