/ Dictionary / Index P pronucleus: Meaning and Definition of Find definitions for: pro•nu•cle•us Pronunciation: (prō-n'klē-us, -ny'-), [key] — pl. -cle•i either of the gametic nuclei that unite in fertilization to form the nucleus of the zygote. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: pronucleus (Thesaurus) pronuclear pronuke Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language