a back number

back number

Someone or something that is out of date, out of fashion, or no longer relevant. Alludes to an issue of a periodical, magazine, or any serial publication that is now out of date. Primarily heard in US, South Africa. While it created quite a controversy in its time, the movie's love scene is a bit of a back number by today's standard. The singer was a huge star in the 1980s, but she's just a back number now.
See also: back, number
Farlex Dictionary of Idioms.

a back number

If you call someone a back number, you mean that they are no longer useful or successful. This veteran jockey showed he was no back number by coming third out of a field of 24. Note: A back number of a magazine or newspaper is an edition of it that was published some time ago and is not the most recent.
See also: back, number
Collins COBUILD Idioms Dictionary, 3rd ed.

a back number

1 an issue of a periodical before the current one. 2 a person whose ideas or methods are out of date and who is no longer relevant or useful.
See also: back, number
Farlex Partner Idioms Dictionary
See also:
  • back number
  • don't jump the gun
  • drum (something) into one's head, to
  • champ at the bit
  • champ at the bit, to
  • crown of thorns
  • tell (one) what (one) can do with (something)
  • tell someone what to do with something
  • tell what to do with
  • can-shaker