The Collaborative International Dictionary
Isocheim
Isocheim \I"so*cheim\ ([imac]"s[-o]*k[imac]m), n. [Iso- + Gr. ?, ?, winter.] (Phys. Geog.) A line connecting places on the earth having the same mean winter temperature. Cf. Isothere.
Wiktionary
isocheim
n. A geoisotherm of equal mean winter temperature.