The act of being a ninja or doing ninja related things, such as jumping building, running with your hands loosely behind you, or climbing up trees and hiding until your "Target" approaches.
He displayed his awesome Ninjaness when he jumped from that K-mart to the Subway.
by Brian the Ninja December 19, 2006
One of the best and most famous fortnite players out there who is idolized by many children.
Josh: yo wanna watch ninja on twitch?

Daniel: No bro, PUBG is sooo much better
by Bathing Grape July 24, 2018
v. move steathily, or in such a mannor as to conceal your actions
I'll just ninja into my cubicle so my boss doesn't notice im late
by Jester of AKs May 29, 2005
The amount of inner ninja possessed by an individual.
That guy has so much ninjaness hes almost like Chuck Noris
by w00000000000t December 21, 2005
A group (ninjas) or single person (ninja) that is trained in the martial arts. They are the coolest thing on the planet and live in competition with pirates.
Ninjas are so cool that I flipped out, kicked my mom in the face and crapped my pants all in one motion.
by MistahTom November 2, 2005
A better N word to use for your boys instead of the nigga word!!!
Bonzi: yo you know Ollie from Dallas
Quinn" Ya thats my ninja!!

by B0NZI June 23, 2007
Someone who can never be seen. Ever. Ninjas do not show up in photographs.
e.g "That guy is a ninja"
"What guy?"
"...I don't know. Where'd he go?"
by AwesomeMccooooooooool December 5, 2009