(noun) To pretend to be dumber than you are or more ignorant. Used as a defense mechanism when people want to get information out of you or when they want you to do something you don't want to. You can pretend you're too stupid to know what they're talking about. The origin of this term is from black slaves trying to get out of punishments.
"The police asked me if I'd seen anyone rob the 7-11 and I just played the dumb nigger and they left me alone."