Can someone tell me exactly what this means
I always thought it meant posting exactly the same time as someone else does.Or getting that message when you click submit - "someone has posted since you pressed submit,you may want to change your content"

Perhaps someone with forum posting knowledge (more than me), can enlighten me?

For the record, and I could be very wrong. I always thought being ninja'ed meant two posting at the exact same time, one being a few milliseconds faster.

But, yes, someone could shed some light on this, because I often get those nag screens saying "so and so has posted before you, are you sure you want to post now?" (paraphrased version).

An American colloquialism with similar signification would be "beaten to the punch". I've never really limited it to case where the forum software requests further confirmation -- Sometimes, owing to slow-wittedness, analytical research, or real-life distraction, several minutes may pass between the ninja post and my own yet I will still post my own response because I've already gone to the effort of writing the post (and may have worded things in differently).

I actually know for a fact that if you start an edit as a thread reply but haven't submitted it yet and someone else submitted one before you finished your edit (it can take several minutes sometimes if I actually add images and such) that you will get ninja'ed, so, it doesn't have to occur at the exact same time; only have to occur if someone submits a response but does so after you started to edit your response; weird, but that's life. I just submit what I typed twice if I see I was ninja'ed.

I read that the first time, Lyle, thinking, what? He submits his posts twice? Why all the duplicating posts? Then I realized of course, you meant, pressing that submit button a second time. I don't know about the rest of you, but that nag screen annoys me, but sometimes it is actually helpful, when you see a posted comment is about to steer the conversation in the wrong direction.

When I'm answering a question about something that requires some thought about the answer I usually type my response then edit it before submitting because my thoughts run ahead of my fingers.

Sometimes it takes awhile to get it all straight.

Anyway, when I finally click the submit button and then discover someone has answered ahead of me, that's when I've been ninja'd. I usually leave my answer and post again saying that I was ninja'd. I think it has to do with hoping the person that posted ahead of me didn't think I was parroting the response.

Yeah I call Ninja'd posting within like a minute after someone else, so if so and so responds then you respond very quickly after them, I would call that a ninja, this can occur in one of two ways, either you are both responding at the same time, or you see there post have your thoughts in mind very quickly, type rather fast, and respond very quickly.

yes and happens often...i usually post the same