Biology. An organism that lives on, in, or with an organism of another species, obtaining food, shelter, or other benefit; (now) spec. one that…

Any of various parasitic sporozoans of the genus Plasmodium, several of which invade human liver and blood cells and cause malaria. Also (in form…

a pathogenic microorganism.

an obligate parasite, unable to exist except in association with its host.

a parasite infesting damaged plants.

Any of a group of eukaryotic microorganisms resembling acellular slime moulds, forming a plasmodial feeding stage and living mainly as…