Meaning of macronucleus

mac•ro•nu•cle•us

Pronunciation: (mak"rō-n'klē-us, -ny'-), [key]
— n. Biol.
  1. 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.