I'm running Ninja
In reference to Call of Duty games, it is a fancy way of saying "Nobody will hear me" when you are sneaking into or out of a house or other building you weren't supposed to leave/enter to begin with.
Buddy: Dude, are you seriously going to come with me later? Won't your parents hear you?
You: Relax, I'm running Ninja up in this biatch.
You: Relax, I'm running Ninja up in this biatch.
I'm running Ninja by AL_PS3 March 2, 2011
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