Argus or Argos [är'gos, –gus] , in Greek mythology. 1. Many-eyed monster, also called Panoptes. He guarded Io after she had been changed into a heifer. After Hermes slew the monster, Hera took his eyes and placed them in the tail of her bird, the peacock. 2. Builder of the Argo. He built the ship on which Jason and the Argonauts (of which he was one) sailed in quest of the Golden Fleece.