infusorian

noun

1. any of a former large group (Infusoria) of microscopic animals found in infusions of decayed organic matter and in stagnant water
2. any of a former class (Infusoria) of protozoans found in most water, characterized by cilia which permit free movement, as paramecia or stentors

Etymology: < ModL (animalcula infusoria), neut. pl. of infusorius, pertaining to infusions (< L infusus: see infuse) + -an

adjective

of this group or class