/ Dictionary / Index N nucleon: Meaning and Definition of Find definitions for: nu•cle•on Pronunciation: (n'klē-on", ny'-), [key] — n. Physics. a proton or neutron, esp. when considered as a component of a nucleus. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: nucleon (Thesaurus) nucleolus nucleonics Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language