microorganism
Definitions
An organism of microscopic size, typically consisting of a single cell.
A microscopic organism, such as a bacterium, virus, or fungus.
Examples
A single microorganism can multiply rapidly under the right environmental conditions.
Scientists use powerful microscopes to study the behavior of each tiny microorganism.
Not every microorganism is harmful; in fact, many are essential for human digestion.
Synonyms
microbe germ bacterium microscopic organism pathogen bug micro-organism