From Longman Dictionary of Contemporary Englishmicrobemi‧crobe /ˈmaɪkrəʊb $ -kroʊb/ noun [countable] HBan extremely small living thing which you can only see if you use a microscope. Some microbes can cause diseases.
Examples from the Corpus
microbe• And each microbe was made up of atoms and molecules.• Prolonged exposure, even to small amounts of genetically-engineered microbes in the air, could cause allergies in workers.• After that, hardly any scientists said life, even microbes, existed on Mars.• Some protein molecules are simply too large for microbes to handle.• Life, in fact, would have been impossible for most higher forms, with only the hardiest microbes surviving.• Infectivity describes the likelihood that a particular microbe will be transmitted under particular circumstances.• Knowing where the microbe struck opened a door to understanding how it might work.• Only within the last few years have doctors begun to realize that this microbe can cause disease.Origin microbe (1800-1900) micro- + Greek bios “life” 