Source : Webster's Revised Unabridged Dictionary (1913)

Equus \E"quus\, n. [L., horse.] (Zo["o]l.)
   A genus of mammals, including the horse, ass, etc.

Source : WordNet®

Equus
     n : type genus of the Equidae: only surviving genus of the
         family Equidae [syn: {genus Equus}]