isotac

[ ahy-suh-tak ]
/ ˈaɪ səˌtæk /

noun

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. 2019