from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A line drawn on a weather map or chart linking all points of equal or constant temperature.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A line of equal or constant temperature on a graph or chart, such as a weather map.

from the GNU version of the Collaborative International Dictionary of English

  • n. A line connecting or marking points on the earth's surface having the same temperature. This may be the temperature for a given time of observation, or the mean temperature for a year or other period. Also, a similar line based on the distribution of temperature in the ocean.
  • n. A line on a graph connecting points representing states having the same temperature; an isothermal line.

from The Century Dictionary and Cyclopedia

  • n. A line connecting points on the earth's surface having the same mean temperature.
  • n. In mathematics, a curve representing phenomena which happen at constant temperature.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. (meteorology) an isogram connecting points having the same temperature at a given time


From French isotherme, having the same temperature : Greek īso-, iso- + Greek thermē, heat; see -therm.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From the French adjective isotherme ("of equal temperature"), itself from Ancient Greek ἴσος (isos, "equal") + θέρμη (thermē, "warmth") (Wiktionary)



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