1. any of various funguslike organisms belonging to the phylum Myxomycota, of the kingdom Protista (or the plant class Myxomycetes), characterized by a noncellular, multinucleate, creeping somatic phase and a propagative phase in which fruiting bodies are produced bearing spores that are covered by cell walls.
2. any of several similar organisms of the phylum Acrasiomycota (or class Acrasiomycetes), differing from the true slime molds in being cellular and nucleate throughout the life cycle.
[ 1875-80 ]