English Etymology From were- + horse. Noun werehorse (plural werehorses) (fiction) A shapeshifter who can assume the form of a horse. 2011, Anthony Francis, Blood Rock, Bell Bridge Books, →ISBN, page 36:“Werehorse,” Gettyson said curtly. “There's no such things as weredonkeys.”Wikiwand - on Seamless Wikipedia browsing. On steroids.