(in modern biological classifications) any unicellular or simple multicellular organism belonging to the kingdom Protoctista, which includes protozoans, algae, and slime moulds
Word Origin
C19: from New Latin protoctista, perhaps from Greek prototokos first born
protoctist in Medicine
protoctist pro·toc·tist (prō'tək-tĭst) n. A eukaroytic, unicellular organism belonging to the kingdom Protoctista, which includes protozoa, slime molds, and certain algae.