/ Dictionary / Index P plankton: Meaning and Definition of Find definitions for: plank•ton Pronunciation: (plangk'tun), [key] — n. the aggregate of passively floating, drifting, or somewhat motile organisms occurring in a body of water, primarily comprising microscopic algae and protozoa. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: plankton (Thesaurus) plankter planned economy Related Content Daily Word Quiz: ablution Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language