lean back vs slant

lean back is not a noun while slant is a noun.

Word	Noun	Adjective	Verb	Adverb
lean back	No	No	Yes	No
slant	Yes	No	Yes	No

As verbs, slant is a hypernym of lean back; that is, slant is a word with a broader meaning than lean back:

Other hypernyms of lean back include angle, lean, tilt, tip.

lean back (noun)	slant (noun)
	degree of deviation from a horizontal plane
	a biased way of looking at or presenting something

lean back (verb)	slant (verb)
move the upper body backwards and down	present with a bias
	to incline or bend from a vertical position
	heel over
	lie obliquely