From Longman Dictionary of Contemporary Englishpass away phrasal verbMXDIEto die – use this when you want to avoid saying the word ‘die’ → pass→ See Verb table
Examples from the Corpus
pass away• And we knew we would never pass away.• It didn't hurt so much as it did with my Dad passing away.• Nyrene had sat up with him all night and was with him when he passed away.• They were like ailing friends met at the post office, or greatly missed because they had passed away.• My wife had just passed away, and I didn't want to be around people.• Have you heard? Carl passed away last night.• The party's old guard -- folks like Mo Udall and Dennis DeConcini -- have passed away or moved on long ago. 