/ Dictionary / Index M macronucleus: Meaning and Definition of Find definitions for: mac•ro•nu•cle•us Pronunciation: (mak"rō-n'klē-us, -ny'-), [key] — n. Biol. the larger of the two types of nuclei occurring in ciliate protozoans, having a multiple set of chromosomes and functioning in cell metabolism and protein synthesis. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. macronucleate macronutrient Related Content Daily Word Quiz: diaphanous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language