Source : Webster's Revised Unabridged Dictionary (1913)

Isogeothermal \I`so*ge`o*ther"mal\, Isogeothermic
\I`so*ge`o*ther"mic\, a.
   Pertaining to, having the nature of, or marking,
   isogeotherms; as, an isogeothermal line or surface; as
   isogeothermal chart. -- n. An isogeotherm.