(nin-juh up) verb. The act of tying a black t-shirt to ones face and doint subversive activities. Usually used when stealing cigarettes or blowing up peoples cars.
Johnny Twobags - Man, Ame has a pack of Newports, but shes asleep and I'd have to crawl over her.

Mr. Dopey - You'd better ninja up and do that shit

*Johnny Twobags ties his shirt up and backflips off the ceiling.
by Lonus the Terror March 11, 2007

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Top Definition
The act of solving any and all problems through the use of voilence and smoke bombs.
Stop crying, ninja up, and hit him or her in the neck with a throwing star."This sentence can be used for any situation."
by bmoten November 13, 2010

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Lotsa space for your liquids.

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Lotsa space for your liquids.

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Your favorite word on a white mug.

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The Urban Dictionary Mug

One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.

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The Urban Dictionary T-Shirt

Soft and offensive. Just like you.

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The Urban Dictionary T-Shirt

Smooth, soft, slim fit American Apparel shirt. Custom printed. 100% fine jersey cotton, except for heather grey (90% cotton).

Buy the t-shirt