Aug 24, 2025 hyacinth ˈhī-ə-(ˌ)sin(t)th 3 syllables rare ‹ noun. a precious stone of the ancients sometimes held to be the sapphire noun. a gem zircon or hessonite noun. a plant of the ancients held to be a lily, iris, larkspur, or gladiolus › Origin Latin hyacinthus, a precious stone, a flowering plant, from Greek hyakinthos.