[ ahy-suh-tak ]
/ ˈaɪ səˌtæk /
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