We don't have synonyms for never event yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are never ever.
(n) :
A serious adverse medical event that should never occur and thus is, by strict definitions of preventability, always preventable, being unambiguous, clearly identifiable and measurable, and resulting in death or significant disability.
(n) :
A particularly shocking preventable medical error that should never occur.
(n) :
A serious adverse medical event that should never occur and thus is, by strict definitions of preventability, always preventable, being unambiguous, clearly identifiable and measurable, and resulting in death or significant disability.
(n) :
A particularly shocking preventable medical error that should never occur.