once in a lifetime

once in a lifetime idiom
Extremely rare, especially as an opportunity. For example, An offer like that will come just once in a lifetime. This phrase, often used hyperbolically, was first recorded in 1854. Also see of one's life.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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