Source : Webster's Revised Unabridged Dictionary (1913)

Protista \Pro*tis"ta\, n. pl. [NL., fr. Gr. prw`tistos first.]
   (Zo["o]l.)
   A provisional group in which are placed a number of low
   microscopic organisms of doubtful nature. Some are probably
   plants, others animals.

Protiston \Pro*tis"ton\, n.; pl. {Protista}. [NL.] (Zo["o]l.)
   One of the Protista.

Source : WordNet®

Protista
     n : eukaryotic one-celled living organisms distinct from
         multicellular plants and animals: protozoa, slime molds,
         and eukaryotic algae [syn: {division Protista}]