I use this term often in my ads and on my website.
To me, an amateur horse is one who deals with less than perfect situation with aplomb. IOW, when you run to the chip, the horse will not only do it, but will canter away without trying to kill you for it. I know that’s not a dressage example, but maybe it’s simpler to define with a hunter/jumper horse? Beyond that, an “amateur horse” is one who is nice to be around on the ground and that wants to be friendly. It may or may not be spooky, but an “amateur horse” isn’t going to try to kill you because it’s scared of something, and personally I don’t consider a horse that has a spook to fall into the "amateur horse category. It should be a relatively simple and straightforward horse, and ideally one that doesn’t “need” a lot of pro rides.
I had an interesting experience this summer when a gal tried one of my horses (again, hunter/jumper example, though the idea is the same applied to dressage). We walked over early and watched her ride the horse she was trying before mine. The horse was stunningly gorgeous, a “10” mover, and absolutely perfect in every way for all of the flatwork. Then the gal trotted a little fence. Perfect again. Then she cantered a fence. The first time she was a little deep (but generally ok) and the horse swung it’s neck a little on the backside. The next time she ATE IT to the little crossrail and that horse landed and did it’s darnedest to buck that lady off…hind feet to the sky style. That’s the opposite of “an amateur horse.”
I’ll share a video of one of my young horses. This is a 12 year old beginner rider at one of her first horseshows. The round is not perfect, and maybe not even terribly good. But this epitomizes the brain that I consider an “amateur-friendly horse.” The kid was a little nervous (this was her first time ever in the Short Stirrups at one of her first ever shows), and it shows, but the horse never reacted to her ride or decisions at all:
https://youtu.be/KdF3V54ED_U
Take out the jumps, and it’s the same principle. When things go sideways (weather, commotion, other horses acting up), the “amateur-friendly” horse takes care of the rider before trying to get out of the situation itself.
And yes, there are lots of amateurs who don’t “require” an amateur-friendly horse. I am an amateur and I prefer a horse that has a bit of a wicked streak. But the ones that I define as “ammy-friendly” sure are a lot more fun to break and train! :lol: