| Noun | 1. | subclass Infusoria - in some recent classifications, coextensive with the Ciliata: minute organisms found in decomposing infusions of organic matterCiliata, Ciliophora, class Ciliata, class Ciliophora - class of protozoa having cilia or hairlike appendages on part or all of the surface during some part of the life cycle infusorian - any member of the subclass Infusoria class - (biology) a taxonomic group containing one or more orders |