/ Dictionary / Index H heat reservoir: Meaning and Definition of Find definitions for: heat' res"ervoir Pronunciation: [key] — Thermodynam. Thermodynam. a hypothetical body of infinitely large mass capable of absorbing or rejecting unlimited quantities of heat without undergoing appreciable changes in temperature, pressure, or density. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. heat rash heat-seal Related Content Daily Word Quiz: abyss Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language