a chance that will never occur again in one's lifetime.
This is a once-in-a-lifetime chance. Don't miss it.She offered me a once-in-a-lifetime chance, but I turned it down.
once-in-a-lifetime chance
A chance or opportunity afforded to one that is or seems unlikely to ever come about again. This is a once-in-a-lifetime chance to manage our European office in Switzerland, so please think about it.I found myself with the once-in-a-lifetime chance to have dinner with the famous author.
once-in-a-lifetime chance
and once-in-a-lifetime opportunity
a chance that will never occur again in one's lifetime. This is a once-in-a-lifetime chance. Don't miss it.She offered me a once-in-a-lifetime opportunity, but I turned it down.