Definition of geotherm in US English:

geotherm

noun

Geology
  • Originally: = "isogeotherm". Now usually: a graph of temperature as a function of depth in the earth's crust; a geothermal gradient.

Origin

Early 20th century; earliest use found in John Joly (1857–1933), geologist and physicist. From geo- + -therm; perhaps originally short for isogeotherm.

Pronunciation

geotherm

/ˈdʒiːə(ʊ)θəːm/