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definitions

isotac

[ahy-suh-tak]
noun
  1. a line drawn on a map connecting all points where ice starts to melt at approximately the same period in spring.

Origin of isotac

iso- + -tac < Greek takênai to melt or takerós melting
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018