melt vs defrost

melt is a noun but defrost is not a noun.

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

As verbs, defrost is a hyponym of melt; that is, defrost is a word with a more specific, narrower meaning than melt:

Other hyponyms of melt include deliquesce, de-ice, deice.

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

melt (verb)	defrost (verb)
become or cause to become soft or liquid	make or become free of frost or ice
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