heat reservoir: Meaning and Definition of

heat' res"ervoir

Pronunciation: [key]
— Thermodynam. Thermodynam.
  1. 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.