/ Dictionary / Index F fusion reactor: Meaning and Definition of Find definitions for: fu'sion reac"tor Pronunciation: [key] a reactor for producing atomic energy by nuclear fusion. Cf. reactor (def. 4). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. fusionism fusobacterium Related Content Daily Word Quiz: ablution Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language