When a person of Japanese origin(a nip) slaps another person. Similar to a pimp slap. Often used to bring shame to the recipient, or to illicit humor from those present who witnessed the nip slap.
Can be used in the past tense, "Nip-Slapped" to indicate that someone got a good old fashion beat-down by a Japanese person.
Damn, did you see how bad Todd nip slapped Jeff when he was passed out drunk like a guppy. How embarrassing! Good thing you got a picture of it.