Unthaw (verb)
To thaw out, to unfreeze; to become soft (of something which had been frozen).
Thaw (verb)
To gradually melt, dissolve, or become fluid; to soften from frozen
“the ice thaws”
Thaw (verb)
To become so warm as to melt ice and snow — said in reference to the weather, and used impersonally.
“It’s beginning to thaw.”
Thaw (verb)
To grow gentle or genial.
“Her anger has thawed.”
Thaw (verb)
To gradually cause frozen things (such as earth, snow, ice) to melt, soften, or dissolve.
Wiktionary
Unthaw (verb)
melt or thaw
“the warm weather helped unthaw the rail lines”
Unthaw (verb)
still frozen
“you can cook prawns from frozen by plunging them, unthawed, into boiling water”
Oxford Dictionary