tilt vs lean back

tilt is a noun but lean back is not a noun.

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

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

Other hyponyms of tilt include incline, pitch, slope, weather, heel, list, recline.

tilt (noun)	lean back (noun)
pitching dangerously to one side
the property possessed by a line or surface that departs from the vertical
a slight but noticeable partiality
a contentious speech act; a dispute where there is strong disagreement
a combat between two mounted knights tilting against each other with blunted lances

tilt (verb)	lean back (verb)
charge with a tilt	move the upper body backwards and down
to incline or bend from a vertical position
heel over
move sideways or in an unsteady way