/ Dictionary / Index H holoplankton: Meaning and Definition of Find definitions for: hol•o•plank•ton Pronunciation: (hol"u-plangk'tun, hō"lu-), [key] — n. plankton that spend their entire life cycle as free-swimming organisms (opposed to hemiplankton). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. holophytic holopneustic Related Content Daily Word Quiz: impetuous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language