The term you are looking for is disaster. A disaster is any unexpected event that threatens lives and may cause significant damage to property, infrastructure, and the environment. Other terms related to this concept include:
- Emergency: A serious, unexpected, and often dangerous situation requiring immediate action.
- Calamity: A disastrous event marked by great loss and lasting distress.
- Crisis: A time of intense difficulty or danger.
- Cataclysm: A violent upheaval that causes significant change or disaster.
Each of these terms has its nuances but generally relates to events that pose serious risks to life and property.