1. Also called green mold. any fungus of the genus Penicillium, which forms a bluish-green, furry coating on foodstuffs inoculated by its spores.
2. Plant Pathol. a. a disease of plants, characterized by necrosis of leaves or fruit and the growth of bluish or grayish mold on affected parts, caused by any of several fungi, as of the genus Penicillium or Peronospora tabacina. b. See downy mildew (def. 2).