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1) Verb: When getting down to the business with a girl, cramping a knick-knack is the sequence of removing her underwear, scratching them, sniffing them, scrunching them up and then throwing them on the floor.

2) The past tense of shtting your pants.
1) Lad 1: Did you bring that chick back last night?
Lad 2: Y'all better know dat! I did cramp a knick-knack.

2) Nicky Nicky Shinder: I just cramped my knick-knack again! Will have to buy some new Primark undies!
by NiftyCreature February 06, 2013