- any fungus of the class Fungi Imperfecti.
- Any of various fungi that reproduce only asexually, by means of conidia. The penicillin mold, the fungus that causes athlete’s foot, and the fungus that causes root rot and damping off in plants are deuteromycetes. The deuteromycetes do not form a natural phylogenetic grouping. Instead, the classification simply includes the fungal species that have lost the sexual stage in their life cycle. Most deuteromycete species are in fact descended from ascomycetes and can be reclassified as such if their sexual stage is discovered. Also called imperfect fungus Compare perfect fungus.