/ Dictionary / Index N nuclear reactor: Meaning and Definition of Find definitions for: nu'clear reac'tor Pronunciation: [key] — Physics. Physics. reactor (def. 4). Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. nuclear reaction Nuclear Regulatory Commission Related Content Daily Word Quiz: mamba Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language