n. Any little animal, as a mouse, insect, etc.n. A minute or microscopic animal, nearly or quite invisible to the naked eye, as an infusorian or rotifer; an animalculum: as, the bell-animalcule, a ciliate infusorian of the family Vorticellidæ; wheel-animalcule, a rotifer; bear-animalcule, a minute arachnidan of the order Arctisca. See cuts under Arctisca, Rotifera, and Vorticella.