back number

back number idiom
Dated, out of style. For example, That hat is really a back number, or The game has changed so fast that a player who returns to the circuit after several years' absence usually finds he or she is a back number. This term originally referred to back issues of periodicals, which are no longer newsworthy. [Late 1800s]

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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