if trick motorcycling is motorcross (mx) and trick cycling is bicycle motorcross(bmx) does that make trick unicycling unicycle motorcross or umx or am i just crazy?
Yeah UMX was used at one point by Pashley to describe their unis.
John Foss is a walking encyclopedia on this. I know he can add much to this discussion, but here is a start.
wouldnt it be TUMX?
trick unicycle motorcross?
dude, i cal my ridin UMX and that’s it
You’re not crazy like me. I call it UMX too. 
Bicycle motocross, or BMX, is a type of racing. A “moto” is a heat, and I think “cross” comes from cross-country though that’s a guess.
When people do tricks on BMX-type bikes it’s often called Flatland BMX, but I think the BMX part is a description of the bike, not the riding. A flatland performance certainly is not BMX. But Flatland BMX is just one type of trick riding on bicycles, and is one of the newest. I do Artistic Cycling, which is the English name for Kunstfahren, the German word for the same basic thing. That sport goes back 80 years or more, directly back to the professional performers who used to do it on stage and in the circus.
The link that was provided above explains why we used to call off-road unicycling UMX. But we don’t anymore. Though I have heard of people doing motocross races on unicycles, I’ve never seen one. Now we call it MUni, and we do it cross country, or uphill, or downhill, or in combinations.
I have a Pashley UMX - a very primitive 20" unicycle with a BMX-style tyre. The model name was used in the 1980s.