Definition of infusoria in US English:


plural noun

  • Single-celled organisms of the former class Infusoria, which consisted mainly of ciliate protozoans.

    • ‘This action is confined, however, to the origins of the most structurally-simple forms of life - infusoria.’
    • ‘But the germs of these infusoria and molds can only come from the air, if the liquid is boiled, because the boiling destroys all those that were present in the container or which had been brought there by the liquid.’
    • ‘Do not worry about overfeeding a little as the dear little ducks will soon polish off any excess bait and the feed itself will attract infusoria and water-borne insects to your swim.’
    • ‘It is possible that the infusoria under the microscope do the same.’


Modern Latin, from Latin infundere (see infuse); so named because they were originally found in infusions of decaying organic matter.