'Protozoan' definitions:

Definition of 'protozoan'

adjective

Of or relating to the Protozoa [syn: protozoal, protozoan, protozoic]

noun

Any of diverse minute acellular or unicellular organisms usually nonphotosynthetic [syn: protozoan, protozoon]

From: GCIDE

Protozoan \Pro`to*zo"an\, a. (Zool.) Of or pertaining to the Protozoa. -- n. One of the Protozoa. [1913 Webster]