A Halloween Slap is the tradition that on every halloween, friends must greet each other with a slap on the arm. Dating back to the Celtic times, when halloween was a religious fesival, priests would slap civilians on the arm to wash their bad spirits away. Over time, as halloween spread to places such as America, the halloween slap has become somewhat of a joke, in order to tease or irritate friends and/or peers.
Jimmy: "Hey"

Clarisse: *hits Jimmy on arm* "A slap on the arm for halloween!"

Jimmy: "Damn, you beat me to the Halloween Slap.. maybe next halloween ey!"
by CDGM October 31, 2011
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