fallback vs disengagement

fallback and disengagement both are nouns.

Word	Noun	Adjective	Verb	Adverb
fallback	Yes	No	No	No
disengagement	Yes	No	No	No

As nouns, fallback and disengagement are synonyms defined as:

fallback and disengagement: to break off a military action with an enemy

Other synonyms of fallback include pullout.

fallback (noun)	disengagement (noun)
to break off a military action with an enemy	to break off a military action with an enemy
	the act of releasing from an attachment or connection