What do you call it when you attempt a mount that you have done a thousand times, miss the mount and clunk your head on the pavement?
I don’t think it qualifies as a UPD. It was certainly unplanned, but I don’t think you can dismount if you haven’t mounted first. Whatever you call it, it sure happens fast.
A flop?
I’d call it “an unfortunate sequence of events.”
“UNM” for “upside-down near mount”? 
Those are all good ones. The black eye is going to be hard to explain.
As a learner I thought it was standard mount
Murphy’s mount.
Hopefully you had an audience too.
I’ve had at least two of these with 20+ watching.
I jump up with a good controlled leap and scream “I’m OK!!!”
It usually gets a couple of chuckles.
Murphy’s Mount! I think that’s it!
No audience for the fall or for the walk of shame home. I was actually bleeding right along my eyebrow and I now have a black eye.
It’s surprising how fast you can fall. I remember jumping up for the mount, and I remember my face hitting the ground, but nothing in between. I wish I had it on video because I don’t even know how it happened.
Anyway, if anyone is wondering if you can attempt a simple, familiar mount and then hit the street so hard with your face that you think you might have cracked the street…yes you can.
Were you wearing a helmet?
No helmet. I have only fallen all the way to the ground maybe 4 or 5 times total and have never come close to hitting my head before. I only ride on the street. The area I hit (side of my face from eyebrow to chin) wouldn’t have been covered by the helmet but a helmet might have taken a little of the impact.
The worst part to me is I wasn’t even riding. I was just attempting to get on.
Was there time to reach out with your hands and break the fall? It sounds like you missed or slid off the second pedal, causing the uni to lurch rearward quickly, making you go straight down, rather than swinging forward / doing a superman.
Most UPDs give us a split second of time to do a little on-the-fly planning. What happened to you might be called an NFID (no freaking idea dismount).
Safety gear: Useless 99.93% of the time!
That is probably what happened. I didn’t even have time for a one syllable swear word.
LOL!
The only time that happened to me was a first attempt at an overgeared giraffe. I assume I lifted myself off the seat, then said seat launched backwards.
Five feet up, and next thing I knew I came to with my dad next to me who was 50’ away. I got radial nerve damage that lasted over a year.
You wouldn’t have hit your eyebrow if you were wearing a properly fitted helmet.
Safety gear… useful 100% of the time.
You’re right. I’m going back to the helmet.
Happened to me last Fall. I was taking a turn and a small jump on a low curb I’d done a dozen times, when the next thing I knew I was on my hands and knees without any sense of transition and a good sense of pain. Concrete is not very giving. Its taken me almost all winter for my one knee to recover.
After having a head injury in the 1980’s I always strive to wear a helmet.
It happened to me last fall on my head. 
The OP didn’t mention what type of mount he was doing, which could be a clue to how it all went wrong.
One of the worst freemounts I’ve ever been witness to (didn’t quite see it but I was right nearby) was the mom of some very notable unicyclists in Alabama. She was just going to ride up and down the track before the little regional meet, that they were hosting, got started. She somehow missed the pedal, went down face first, got taken away, and came back with large bandages on both knees, a splint on one arm and I a cast or a sling on the other. She had jammed an elbow, and I think broken the opposite wrist. Later in the day, her son (Dale Granberry) also had a bad crash, and I think he also went to the emergency room (where I think they knew him by name). Fun times!
It was a rolling mount on a 29er, jumping on with the right pedal to the rear and left pedal to the front (3 and 9 position). I fell on my right side, I’m guessing straight down, with most of the force on my head between my right eyebrow and cheek bone. I saw stars like in the cartoons.
That’s why I don’t like rolling mounts, it always makes me see the word DANGER in my head each time I just think about attempting it.
- it doesn’t let you place your feet on the pedals exactly where you want it to be, so you have to move them while pedaling, which can also lead to the same epic fall, especially on a 36er.
Even for the normal freemount, I préfère freemounting to the top of the unicycle, then I do 2 or 3 hops, and then start to pedal.
Thus I need a smaller impulsion than if you wanted to pedal directly after the freemount.
Once again on a 36er with 150 or 137 it saves some energy and prevent me from jumping too much and missing the front pedal. + this smaller jump let’s me more time to place my second foot on the front pedal like I want.
Not mounting in my case, but I had a similar fall very recently when learning to ride backwards. Was just transitioning and the wheel stayed still when I tried to pedal (or at least that’s what I assume, don’t really have a proper memory of it) - I went straight down on my back without any time to break the fall. Banged my head and gave myself a slight concussion - a tingly feeling in my arms for a few seconds and didn’t feel too steady on my feet when I got up.
No I wasn’t wearing a helmet - I do mostly now when practicing riding backwards, but still mostly don’t and not interested in a debate on that.
Don’t have a 36er, but often rolling mount my 29er - it’s fun and hasn’t gone wrong yet (I’m not generally that bold, so tend to bail out if it doesn’t seem quite right - always have for everything since learning to ride, which might have meant I don’t progress so fast, but it does seem preferable to my son who seems to hang on trying to save it rather than landing on his feet most of the time!)