Though it sounds unlikey, this term is actually used for the offspring of a donkey and a zebra. Also called a zebrass. Horses, donkeys and zebras can all interbreed, though they usually produce sterile offspring.

A real animal. Stop downvoting AT, please. (Or at least cut out the obnoxious softlinks. You could check this stuff out BEFORE you do stuff like that.) I'll add more as I find out more.

AKA a zeedonk or a zebrass.
They tend to look like sleek donkeys with stripes on their legs, necks and backs. They are apparently not viable.