reversal vs undoing

reversal and undoing both are nouns.

Word	Noun	Adjective	Verb	Adverb
reversal	Yes	No	No	No
undoing	Yes	No	No	No

As nouns, undoing is a hyponym of reversal; that is, undoing is a word with a more specific, narrower meaning than reversal:

reversal (noun)	undoing (noun)
a change from one state to the opposite state	an act that makes a previous act of no effect (as if not done)
the act of reversing the order or place of	loosening the ties that fasten something
turning in the opposite direction
a major change in attitude or principle or point of view
a judgment by a higher court that the judgment of a lower court was incorrect and should be set aside
a decision to reverse an earlier decision
turning in an opposite direction or position
an unfortunate happening that hinders or impedes; something that is thwarting or frustrating