1.any member of the kingdom of living things (as mushrooms, molds, and rusts) that have no chlorophyll, must live in or on plants, animals, or decaying material, and were formerly considered plants
2.any of the kingdom Fungi of saprophytic and parasitic spore-producing eukaryotic typically filamentous organisms formerly classified as plants that lack chlorophyll and include molds, rusts, mildews, smuts, mushrooms, and yeasts