n. a term used for a white girl's hair that has a texture/consistency the same as or similar to a black girl's hair.
(often used as an exaggeration for hair frizzed out by humidity, or just for natural texture.)
White Girl: *brushes thick, nappy hair furiously*
Black Girl: "Are you okay?"
White Girl: "NO! I have 'NILLA NAPS!"
Black Girl: "SHH! We're in the subway! You'll get us shot..."