(verb) to mess with a member of the opposite sex's head, usually by women. Originates from the comedy routine of comedian Dane Cook.
"Peter needed to talk after Maria brain-ninja'd him."
by strongbadia7 November 13, 2007
when your in a horrible "relationshit" and you get in a fight one day and the girlfriend happens to say a comment that will seem at first like the worst come back ever but soon will make you so friggin' angry that you go make a ass out of yourself in front of her
yeah steve i completely was fucking brain ninja'd, i walked in and just sounded like a complete dumm shit
by dickydick May 14, 2007