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1.
A half peeled banana must be shoved into the targets face where the fruit must be smeared as quickly as possible. Then you must retract and once again swing the banana peel toward the face to achieve proper contact and satisfying snap sound of the peel against the flesh. It is important to note that this is not a bully's activity; the target should never be victimized, but deserving of a banana slap. it is an underdogs activity. Most often perpetrated by the victim to a bully. The target must be fully deserving of the insult. Then, like Braveheart you must scream "banana slap!"
Target: Give me your lunch money.

Hero: I can't do that, but I can give you this... ...Banana slap!

blurn

Google blurn or banana slap for video tutorials or more examples.
by Ballistic2010 December 14, 2010
 
2.
First you eat a banana, then you take the peal, grab the connected end, and slap someone with the separated end. 3 or more ends will suffice in causing enough pain and hilarity. When you banana slap someone, you must yell, "banana slap!" This is only necessary for the complete experience.
*eats banana*
*grabs end*
*slaps*
*yells, "banana slap!"*
*runs away if necessary*
by The Buhjohnston March 07, 2005