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.
von Brian the Ninja 19. Dezember 2006
The amount of inner ninja possessed by an individual.
That guy has so much ninjaness hes almost like Chuck Noris
von w00000000000t 20. Dezember 2005