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.
af Brian the Ninja 19. december 2006
Can you define these popular missing words?
The amount of inner ninja possessed by an individual.
That guy has so much ninjaness hes almost like Chuck Noris
af w00000000000t 20. december 2005