/ Dictionary / Index F fissionable: Meaning and Definition of Find definitions for: fis•sion•a•ble Pronunciation: (fish'u-nu-bul), [key] — adj. Physics. capable of or possessing a nucleus or nuclei capable of undergoing fission: a fissionable nucleus; fissionable material. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: fissionable (Thesaurus) fission fission bomb Related Content Daily Word Quiz: diligent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language