A word from the plains of Colombia and Venezuela: "caballo realengo." It appears in song lyrics, and a friend used it writing me from Colombia, about a horse. Here is the quote:
....esta es la primera vez que ensillo a quitapesares, el caballo mas realengo que habita en estos lugares.....
I translate "This is the first time I have saddled quitapesares, the (wildest) horse around here."
The machine says "ownerless" or "idle, free, unattached". I'm guessing woildest" would be the right translation in context.
Thanks for your thoughts.