I know this horse, and nobody knows what breed he is. There's about 20 horses with him and every horse except a few are mixed breeds. The horse I'm talking about has so many different breeds that there is probably no telling what he is. Would you be able to consider this a Mustang? I know some people think a Mustang has to be gathered from the range or born from a Mustang that was off the range, etc. But I've heard people say that after so many breeds mixed into one horse it can be called a Mustang. Just curious to know what others think on this. Thanks! :)

 No, that is not the case.  A horse who is a mix of many breeds is simply a grade horse.

A "mustang" is generally considered to be a feral horse who has lived in the wild.  They are also a mix of a variety of breeds, as horses have been released into wild herds for several centuries to change the look and movement -- draft horses, cavalry mounts, thoroughbreds, arabians, quarter horses, just to name a few, have all contributed blood to the American mustang herds, so the phrase "purebred mustang" is a bit of an oxymoron.