unthaw vs melt

unthaw is not a noun while melt is a noun.

Word	Noun	Adjective	Verb	Adverb
unthaw	No	No	Yes	No
melt	Yes	No	Yes	No

As verbs, unthaw and melt are synonyms defined as:

Other synonyms of unthaw include dethaw, dissolve, thaw, unfreeze.

unthaw (noun)	melt (noun)
	the process whereby heat changes something from a solid to a liquid

unthaw (verb)	melt (verb)
become or cause to become soft or liquid	become or cause to become soft or liquid
	reduce or cause to be reduced from a solid to a liquid state, usually by heating
	lose its distinct outline or shape; blend gradually
	become more relaxed, easygoing, or genial
	become less clearly visible or distinguishable; disappear gradually or seemingly
	become less intense and fade away gradually