From Longman Dictionary of Contemporary Englishdie out phrasal verbDISAPPEARto disappear or stop existing completely The wild population of koalas is in danger of dying out. There will be outbreaks of rain, gradually dying out later. → die→ See Verb table
Examples from the Corpus
die out• Diseases such as leprosy and polio have almost completely died out.• Many of the old village traditions are dying out.• The country is changing very quickly and many of the old traditions are dying out.• Unless we do something now, hundreds of plant and animal species will die out.• The nearest common ancestor of man and the modern great apes died out about 30 million years ago. 