A natural and unavoidable catastrophe that interrupts the expected course of events WordNet 3.0 & Open English WordNet

In contract law, force majeure is a common clause in contracts which essentially frees both parties from liability or obligation when an extraordinary event or circumstance beyond the control of the parties, such as a war, strike, riot, crime, epidemic, or sudden legal change prevents one or both parties from fulfilling their obligations under the contract. Wikipedia

In legal usage in the English-speaking world, an act of God or damnum fatale is a natural hazard outside human control, such as an earthquake or tsunami, for which no person can be held responsible. Wikipedia

Common clause in contracts that frees parties from legal obligation when an extraordinary event or circumstance occurs. Wikipedia Disambiguation

Contract clause regarding extraordinary occurrence beyond control which prevents one or both parties from fulfilling their obligations Wikidata

Usually-natural disaster outside human control, for which no person is at fault Wikidata

A non attributable impossibility to redeem an obligation. OmegaWiki

An unforeseen occurrence beyond one's control, such as a natural disaster. Wiktionary

Unforeseen occurrence. Wiktionary (translation)

An unavoidable catastrophe, especially one that prevents someone from fulfilling a legal obligation. Wiktionary

Unavoidable catastrophe. Wiktionary (translation)

A greater force; "act of God"; unavoidable accident. Wiktionary