| Noun | 1. | Claviceps purpurea - a fungus that infects various cereal plants forming compact black masses of branching filaments that replace many grains of the plant; source of medicinally important alkaloids and of lysergic acidClaviceps, genus Claviceps - fungi parasitic upon the ovaries of various grasses rye ergot - a sclerotium or hardened mass of mycelium fungus - an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia |