When a person who isn't black acts "black" around certain people.
This person doesn't usually do this, but in certain predicaments he/she flips a theoretical switch; The Nigga Switch, and acts "black," or in some situations, he/she may go "apeshit" on someone's ass.
Tom: Hi Guys What's going on?
*Person of Color Walks in Room*
Tom: Sup Nig?
Person of Color: I See Tom flipped the Nigga Switch