/ Dictionary / Index T thermonuclear reaction: Meaning and Definition of Find definitions for: thermonu'clear reac'tion Pronunciation: [key] — Chem., Physics. Chem.,Physics. a nuclear-fusion reaction that takes place between the nuclei of a gas, esp. hydrogen, heated to a temperature of several million degrees. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. thermonuclear bomb Thermopane Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language