Definition of protists:
(n) :
(microbiology) Any of the eukaryotic, usually unicellular organisms—including protozoans, slime molds and some algae—historically grouped into the kingdom Protista (or Protoctista), now distributed over several clades; any eukaryote that is not a plant, animal or fungus.
(n) :
Any single-celled eukaryote .
(n) :
Any single-celled eukaryote or prokaryote .
(n) :
Any single-celled eukaryote, prokaryote or sponge .