sit back vs slow down

sit back and slow down both are verbs.

Word	Noun	Adjective	Verb	Adverb
sit back	No	No	Yes	No
slow down	No	No	Yes	No

As verbs, slow down is a hypernym of sit back; that is, slow down is a word with a broader meaning than sit back:

Other hypernyms of sit back include decompress, loosen up, relax, unbend, unwind.

sit back (verb)	slow down (verb)
settle into a comfortable sitting position	become less tense, rest, or take one's ease
be inactive or indifferent while something is happening	lose velocity; move more slowly
	become slow or slower
	reduce the speed of
	cause to proceed more slowly