- microscopic organism such as an amoeba or paramecium
- Animalcule ("little animal", from Latin animal + the diminutive suffix -culum) is an older term for a microscopic animal or protozoan. ...
- A minute animal: generally applied to those visible only by the microscope.
- microbe. "Had the animalcule of the itch been endowed with reason they would have quit their entrenchments . . ." (111).