Breadcrumb Home > Dictionary > Index U uranium 235: Meaning and Definition of Find definitions for: uranium 235 Pronunciation: [key] — Chem. Chem. the radioactive uranium isotope having a mass number of 235, comprising 0.715 percent of natural uranium. When bombarded with neutrons it undergoes fission with the release of energy. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. uranium uranium 238 ✖ Related Content Daily Word Quiz: nabob Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language