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slang Something that is very outdated or totally forgotten (often in favor of a more recent development). Oh, Jack is ancient history, we broke up weeks ago! Her interest in photography is ancient history now that she's started doing yoga.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
Fig. someone or something from so long ago as to be completely forgotten or no longer important, as a former relationship. Bob? I never think about Bob anymore. He's ancient history. His interest in joining the army is now ancient history.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
A past event, as in She's talking about her sea voyage, but that's ancient history, or And then there was his divorce, but you don't want to hear ancient history. This hyperbolic idiom transfers the field of ancient history to a much-repeated tale.
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.
n. someone or something completely forgotten, especially past romances. (see also history.) That business about joining the army is ancient history.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.