Ninjasation 

To interrupt and join a conversation with the participants unaware you have joined.

Conversation between more than 2 people and the person having the "ninjasation"

Ninjasation by Almighty Adam and Awesome Ryan February 25, 2011

Ninjamation

The guestamation of a fuckin' Ninja.

"That ninja has some badass ninjamation skills, he ninjamated the exact time that dude was gonna get punched in the face!"

Ninjamation by ThatNinja January 2, 2011

Ninjabation 

Noun

The act of masturbating in public or in front of someone without them noticing or getting caught.

I masturbated in the back seat of the car on the way to the movies....nobody noticed. That was some nice ninjabation.

Ninjabation by donkeygorilla October 31, 2011