defrost vs melt

defrost is not a noun while melt is a noun.

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

As verbs, melt is a hypernym of defrost; that is, melt is a word with a broader meaning than defrost:

Other hypernyms of defrost include dethaw, dissolve, thaw, unfreeze, unthaw.

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

defrost (verb)	melt (verb)
make or become free of frost or ice	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