what is microorganisms
Microorganism. Definition. noun, plural: microorganisms. An organism that is microscopic or submicroscopic, which means it is too small to be seen by the unaided human eye. Supplement.Microorganisms were first observed by Anton van Leeuwenhoek in 1675 using a microscope of his own design.oun, plural: microorganisms. An organism that is microscopic or submicroscopic, which means it is too small to be seen by the unaided human eye. Supplement. Microorganisms were first observed by Anton van Leeuwenhoek in 1675 using a microscope of his own design.