Definition of "isothermal" [i•so•ther•mal]

• Of, relating to, or indicating equal or constant temperatures. (adjective)
• Of or designating changes of pressure and volume at constant temperature. (adjective)
• Of or relating to an isotherm. (adjective)
• An isotherm. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "‘isothermal’ is quite of modern invention; but what a long story it would be to tell the meaning of ‘_isothermal_ lines’, all which is summed up in and saved by the word."
• "The lines called isothermal, that is, lines of equal annual heat, are, therefore, of greatest importance to public economy, because the “zones of production” depend mainly on them. ("
• "Republicanism, will _inevitably_ control the Mississippi river and master the destinies of all soil above the so-called isothermal line, and probably of much below it."