The act of quickly minimizing a computer window when
someone else enters the room because they
do not want the other person to see the contents of
the window, especially if one is looking at porn on their computer.
Dr Venture: "Brock, what did you just ninjamize?"
Brock: "Uhh, I didn't ninjamize anything."
*Dr Venture walks around to Brock's computer to get a look for himself*
Dr Venture: "Ohh my God Brock! more porn?"
Ryan: "Where have you been?"
Josh: "Sorry I had to ninjamize my
World of Warcraft window because my mom came in my room and I'm not
supposed to play
right now."