Definitions for "Protista"
A provisional group in which are placed a number of low microscopic organisms of doubtful nature. Some are probably plants, others animals.
Organisms in this Kingdom are unicellular and have a true nucleus (eukaryotic). They may be heterotrophic or autothrophic (able to make their own food). They may also be motile or sessile.
The third kingdom, next to the kingdoms of plants and animals, in the classification of living organisms. The Protista include all organisms that do not have any extensive development of tissues, such as algae, fungi, protozoa and bacteria.