the act of sneaking up behind a female and hitting them in the vagina. Works best while walking up the stairs behind them. You can use a closed fist or an open palm.
Guy: *walking up stairs behind girl, hits her in the vag*
Girl: Ow! What was that for?!
Guy: Nothing... I just wanted to Ninja Twat you.
Girl: Ow! What was that for?!
Guy: Nothing... I just wanted to Ninja Twat you.
by ilovebirchbeer_not April 28, 2009