unwind vs sit back

unwind and sit back both are verbs.

Word	Noun	Adjective	Verb	Adverb
unwind	No	No	Yes	No
sit back	No	No	Yes	No

As verbs, sit back is a hyponym of unwind; that is, sit back is a word with a more specific, narrower meaning than unwind:

Other hyponyms of unwind include veg out, vegetate, take it easy.

unwind (verb)	sit back (verb)
become less tense, rest, or take one's ease	settle into a comfortable sitting position
cause to feel relaxed	be inactive or indifferent while something is happening
separate the tangles of
reverse the winding or twisting of