/ Dictionary / Index I isothermal: Meaning and Definition of Find definitions for: i•so•ther•mal Pronunciation: (ī"su-thûr'mul), [key] — adj. occurring at constant temperature. pertaining to an isotherm. —n. an isotherm. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: isothermal (Thesaurus) isotherm isothermal process Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language