Isotac definitions

Isotac

1) Glacier melting line
Found on https://www.crosswordclues.com/clue/isotac

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isotac

line joining points where the ice melts at the same time of year
Found on http://phrontistery.info/i.html

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isotac

a line drawn on a map connecting all points where ice starts to melt at approximately the same period in spring.
Found on https://www.infoplease.com/dictionary/isotac

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