once in a lifetime

idiom

Definition of once in a lifetime

: very rare or very rarely a once-in-a-lifetime opportunity This sort of opportunity comes along once in a lifetime.

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“Once in a lifetime.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/once%20in%20a%20lifetime. Accessed 9 Jul. 2020.

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