GNU Collaborative International Dictionary of English

Found one definition

      
Isotherm (?), n. [Iso- + Gr.  heat, fr.  hot.]
1. (Phys. Geog.) 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.

[1913 Webster]


2. (Physics) A line on a graph connecting points representing states having the same temperature; an isothermal line.

[PJC]

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