vis major vs unavoidable casualty

vis major and unavoidable casualty both are nouns.

Word	Noun	Adjective	Verb	Adverb
vis major	Yes	No	No	No
unavoidable casualty	Yes	No	No	No

As nouns, vis major and unavoidable casualty are synonyms defined as:

vis major and unavoidable casualty: a natural and unavoidable catastrophe that interrupts the expected course of events

Other synonyms of vis major include act of God, force majeure, inevitable accident.

vis major (noun)	unavoidable casualty (noun)
a natural and unavoidable catastrophe that interrupts the expected course of events	a natural and unavoidable catastrophe that interrupts the expected course of events