zombie-apocalypsehttp://www.oed.com/dictionary/zombie-apocalypse_n%3Ftab%3Dmeaning_and_usezombie apocalypse, n.
First published 2021

zombie apocalypsenoun

  1. 1982–
    An imaginary event (as in a film, etc.) in which the world is taken over by zombies.
    1. 1982
      Worldwide fears of a zombie apocalypse are growing rapidly.
      Monthly Film Bulletin January 229/1
    2. 2020
      Jack and his friends fight for their lives through the zombie apocalypse.
      New York Times (Nexis) 15 November (Late Final edition)

Originally published as part of the entry for zombie, n.

zombie apocalypse, n. was first published in 2021.