The act of writing a phrase, most commonly "Ninja Post," on a Facebook wall post and deleting it after someone has commented on it.
Dude, I'm putting a ninja post on everyone's status.
Noun - A post the sneaks in before another on a message board. Replying to the same post, and often contain the same message.
Chris: Is DDR3 and DDR2 compatible with each other? - 18 minutes ago.
Tom: No. - 3 minutes ago.
Bob: Nope. - 3 minutes ago.
L33Tjack: haha Bob is pwnd by a Ninja post! xD - 0 minutes ago