I think we use the word "crazy" pretty loosely, kind of like the word "love". However, you usually know when you REALLY love something, so just the same, you'll probably know when/if your horse is REALLY crazy.
Other than that, having never encountered one, I can't give you more specific details
I've only ever seen one horse who I would truly consider "crazy." He was an older grade gelding, mid-teens age wise, I'd guess, and a friend of mine used him for 4-H gaming for a year (my friend was "between" trained horses at the time). That horse was a gem on the ground, just an absolute sweetheart to be around. He could be tacked up with no fuss, nicely accepted the bit, girthing, etc.
That gelding could be relied upon to absolutely explode every single time someone put their foot in the stirrup. Like flipping a switch, Jekyll to Hyde. Saddle didn't matter, bridle/bit didn't matter, weather/season/location didn't matter, every rider every time an explosion of bucking, bolting, running sideways into whatever happened to be there. That horse would run and carry on until he fell down rather than calm down. My friend tried to just ride him out once, just let him run in an open field, and after half an hour of straight crazy had to spiral him down small enough to bail off and go back to the barn.
A typical gaming pattern ran thus: Lead horse to gate, clear innocent bystanders away, and quickly and carefully climb aboard. Use gate to funnel horse into ring, and hope for the best. On a good day, he could be pulled by one rein at a time around barrels, and circled to a relatively slow sideways hop at the end of the run. A bad day, well... lots of time penalties.
I've seen a lot of spoiled horses, a lot of minor problems, a few major problems, a lot of "mad gamers," and that one that I would classify as crazy.
There was a mare that my friend got, Shawnee, and we're starting to think that she's "crazy". We don't know WHAT happened to her, but someone really f---ed her up. A lot of money has gone into her, countless trainers, and tons of time. She's only improved slightly. You can just see in her eyes... She's different. Something isn't there. It took a while for Cricket and I to warm up to eachother, but there was that light in her eyes... This little mare just has a sort of vacant sign. You can't look into her eyes. I can't explain it, it's weird.
Theres a "crazy" mare at this barn im at. Shes gotten worse since no one is working her. But she is ALWAYS slinging her head at turnout time,feeding time, a horse is to close...She was an ok horse with regular ground work and great out on trails. The b/o always said she was loopy. And now she will run you over, go through fences. You cant halter her without her pawing at your foot. Or some times when you go into the stall to get her she will start to circle and either start the head thing or paw. Ive always had a hard time handling her. But now I just feel bad for the mare.
You know, on second thought, I HAVE dealt with a possibly crazy horse.
She has since left the barn I board at, but while she was there, the first thing the BO told me on the tour of the place was "we have the shavings pile in front of her stall to remind people to not go near her" because she lunged out at any passerby and attempted to bite them! There were only two people in the barn who could consistantly turn her out. Her mommy, and the English trainer, who has since left. The BO had her days, and sometimes she would say "she has that look, I'm not going near her". She was an arabian I believe, and came from an abusive home. She looked very smooth to ride, the few times I saw her mom on her, and it was very obvious they had a deep relationship, even though she still had LOTS of kinks that had to be worked out. Her owner often ground drove her before mounting up to see what kind of mood she was in.
When i used the word crazy, i couldn't think of any other words. We throw this word around a lot, and I've always wondered what makes a horse truley crazy (unruly, dangerous...ect) But thank you for the stories! They really do explain it well!!
I've only come into contact with a "crazy" horse once. She had that look that Thatgirlsacowboy described, someone was home but the light was out.
She was replacement horse at my camp, that I volunteer at, and she seemed great for the first 4 days. We took her on trail rides as a group of wranglers and alone to "make sure" how she would behave and she passed our tests with flying colors.
But then, the first day we were letting campers ride her, the horse (the horses are mounted while tied becuase 12 po-ed horses vs 3 wranglers, and 10 kids that don't know what to do, not a good combo) next to her slipped his bridle and jumped back very gently and calmed right down. She (we had already put a kid on her too) jumped back and started bucking, literally like those bucking horses-just like them, and then the kid on her back fell off and she tried to JUMP ON the kid who fell off. I was sure I was watching someone die but somehow this horse's hooves went into the kid's armpits instead of landing on her chest. The horse only stopped bucking once the kid came off. It was one of the scariest things I have ever seen.
We sent that horse away, needless to say. Maybe she was drugged or something, I don't know.
A friend of mine owned horse who was diagnosed with schizophrenia. Seriously. The vet had put the horse on anti-psychotics.
The horse be fine and then act like she heard something, but nothing would be there. Then she'd completely freak out and do things like rear and flip over backwards, or run through any solid object that happened to be in her way. The only way to be safe around the horse was to keep her on the horsey clozerpine, which was EXPENSIVE. They eventually sold the mare to someone who was willing to take her on and better able to maintain her costly drug regimen.