thaw vs defrost

thaw is a noun but defrost is not a noun.

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

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

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

thaw (noun)	defrost (noun)
a relaxation or slackening of tensions or reserve; becoming less hostile
warm weather following a freeze; snow and ice melt
the process whereby heat changes something from a solid to a liquid

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