olemus
äkiline vägivaldne keskkonnamuutus, mille põhjustab
mitte inimtegevus, vaid loodusnähtus
(ujutus, maavärin, orkaan)

Wiktionary:
1. any natural phenomenon that causes great damage and loss of life
2. the emergency situation that is the consequence of such an event

määratlusi
USA:
https://www.dhs.gov/natural-disasters

European Environmemt Agency:
https://www.eea.europa.eu/help/glossary/eea-glossary/natural-disaster

Eestis:
https://www.ilmateenistus.ee/ilmatarkus/kasulik-teada/loodusonnetused/

https://est.agromassidayu.com/chto-takoe-bedstvie-stihijnoe-stihijnie-bedstviya-i-ih-klassifikaciya-news-893455

ülevaateid
https://en.wikipedia.org/wiki/Natural_disaster

https://en.wikipedia.org/wiki/List_of_natural_disasters_by_death_toll

https://ourworldindata.org/natural-disasters

https://www.unocha.org/our-work/coordination/un-disaster-assessment-and-coordination-undac