WordNet sense 1 (the process whereby heat changes something from a solid to a liquid):

thaw, melting, thawing

WordNet sense 2 (reduce or cause to be reduced from a solid to a liquid state, usually by heating):

run

WordNet sense 3 (lose its distinct outline or shape; blend gradually):

meld

WordNet sense 4 (become or cause to become soft or liquid):

dissolve, unfreeze, dethaw, unthaw

WordNet sense 5 (become more relaxed, easygoing, or genial):

mellow, mellow out

WordNet sense 6 (become less clearly visible or distinguishable; disappear gradually or seemingly):

fade

WordNet sense 7 (become less intense and fade away gradually):

disappear