microorganismo

(virology) ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein

(microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered to be plants

a minute life form (especially a disease-causing bacterium); the term is not in technical use

any disease-producing agent (especially a virus or bacterium or other microorganism)

any of the unicellular protists

any of diverse minute acellular or unicellular organisms usually nonphotosynthetic

primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves