act of God vs disaster

act of God and disaster both are nouns.

Word	Noun	Adjective	Verb	Adverb
act of God	Yes	No	No	No
disaster	Yes	No	No	No

As nouns, disaster is a hypernym of act of God; that is, disaster is a word with a broader meaning than act of God:

act of God: a natural and unavoidable catastrophe that interrupts the expected course of events
disaster: an event resulting in great loss and misfortune

Other hypernyms of act of God include calamity, cataclysm, catastrophe, tragedy.

act of God (noun)	disaster (noun)
a natural and unavoidable catastrophe that interrupts the expected course of events	an act that has disastrous consequences
	an event resulting in great loss and misfortune
	a state of extreme (usually irremediable) ruin and misfortune