heat reservoir

noun Thermodynamics.
  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.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for heat reservoir

Historical Examples of heat reservoir

  • He had to pump that heat into a heat-reservoir—a water tank probably—to protect himself.

    The Ultimate Weapon

    John Wood Campbell