isochasm

[ahy-suh-kaz-uh m]

noun Meteorology.

a line on a map or chart connecting points where auroras are observed with equal frequency.

Origin of isochasm

First recorded in 1880–85; iso- + chasm
Related formsi·so·chas·mic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019