act of God vs unavoidable casualty

act of God and unavoidable casualty both are nouns.

Word	Noun	Adjective	Verb	Adverb
act of God	Yes	No	No	No
unavoidable casualty	Yes	No	No	No

As nouns, act of God and unavoidable casualty are synonyms defined as:

act of God and unavoidable casualty: a natural and unavoidable catastrophe that interrupts the expected course of events

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

act of God (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