Technically that’s a fall. You fell down. But that’s boring, how do we fit it into our nerdly arse-covering terminology for the lack of staying on the uni? In the situation described above, BPD would stand for Botched Planned Dismount. Or a UPD with extra style points, if you like. 
In the real world, I mostly use “fell off” in conversation, for obvious reasons. By that I mean, not wanting to explain what a UPD is, and why we have to make up a TLA for falling off!
In response to the occasional UPD around people, they ask “Are you alright/ok?”
I say that I am fine and at least I landed on my feet!
I sometimes have to explain UPDs to MTB’s and other people who ask how many times I have fallen off.
The quickest response is to say, “Loads of times!”
Exactly! If you’re not falling off then you’re not riding hard enough stuff. Generally if I havn’t fallen it’s because i can only find really boring terrain…
My response to such a question is usually along the lines of “You mean today? Otherwise I can’t count that high.” 