(n.) An animal, invisible, or nearly so, to the naked eye. See Infusoria.
(n.) A small animal, as a fly, spider, etc.
Example Sentences:
(1) It is particularly appropriate for an assemblage of protozoologists to pay homage to this intrepid "philosopher in little things," a man with an insatiable curiosity about his wee animalcules, on the tricentenary of his discovery of them, since it was an event of such long-lasting significance.