How about...
"Act of supernatural force beyond the understanding and control of human entities."
OR:
"Operation of extraordinary natural force"
OR:
"A natural event, not preventable by any human agency."
OR:
"Caused by forces of nature, without the possibility of prevention by humans."
An athiest once asked me "If God had created all of us in his image, then why are you so fat?"
I said that "Yes, I'm fat... and you're ugly.
I can lose weight."