Meteorology. a line on a weather map or chart connecting points having equal temperature.
Also called isothermal line. Physics. a curve on which every point represents the same temperature.

1855–60; back formation from isothermal Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
isotherm (ˈaɪsəʊˌθɜːm)
1.  a line on a map linking places of equal temperature
2.  physics a curve on a graph that connects points of equal temperature

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
isotherm   (ī'sə-thûrm')  Pronunciation Key 
A line drawn on a weather map connecting points that have the same temperature. Each point can mark one temperature reading or an average of several readings.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


line drawn on a map or chart joining points with the same temperature. Isotherms are commonly used in meteorology to show the distribution of temperature at the Earth's surface or on a chart indicating constant level or constant pressure. They are also used to show the time variation of temperature with height in the atmosphere or with depth in soil or water; the characteristics of heat flow into soil, for example, are easily visualized from a graph showing temperature as a function of depth and time. A convenient way to compare thermal climates is to plot the temperature for each location as a function of time of day (vertical axis) and time of year (horizontal axis)

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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