One of three monsters, sisters with sharp fangs and hair of venomous snakes (6)

(Other definitions for gorgon that I've seen before include "In Greek myth, a snake-haired woman whose look turned watcher to stone" , "Mythical Greek woman with snakes as hair" , "She had the power to turn people to stone" , "Mythical female winged monster" , "Mythical woman turning people to stone" .)