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Webster 1913 Edition

Noun.

[

Iso-

+ Gr. [GREEK] cold.]

(Phys. Geog.)

A line connecting points on the earth’s surface having the same mean temperature in the coldest month of the year.

isocryme ‎(plural isocrymes)

A line connecting points on the Earth's surface having the same mean temperature in the coldest month of the year.