To stealthily edit published online content after the fact, correcting a mistake - either factual or grammatical in nature - after a commentator has called out said mistake (usually in the comments section) without the original author acknowledging that an error has occurred.
What happened to the part in this article about (erroneous element)? It's totally gone!
Dude, the author ninjaed that part already.
Getting 'ninjaed' in Halo 3, is when somebody jumps backwards over your head and assassinates you.
I got a boner after I ninjaed these two guys in a row.
When someone quickly takes something without anyone else noticing. Pick Pocketing
Jimmy: Where did my cell go?
Kevin: Adam just Ninja'ed it
1. Generally used in online gaming, describes the action of completly disspearing from someone's sight while fighting him. After the person dissapears, he generally owns the guy he dodged.
Holy crap dude! That guy just Ninja-ed me. WTF
To take a knife or sword and to pierce it through the body of a human
Holy cows, Jakie ninjaed my math teacher!
When a person succsessfully clips a black binder clip to your clothing.
"Dude you got a binder clip on your shirt you got ninjaed"