Hyacinthus Syllabification: (Hy·a·cin·thus)Pronunciation: /ˌhīəˈsinTHəs/ Greek MythologyDefinition of Hyacinthus a beautiful boy whom the god Apollo loved but killed accidentally with a discus. From his blood Apollo caused the hyacinth to spring up. Hyacinthus in other Oxford dictionaries Definition of Hyacinthus in the British & World English dictionary