fall-back

/F AO1 L B AE1 K/
noun
  1. 1

    An act of falling back.

  2. 2

    A backup plan or contingency strategy; an alternative which can be used if something goes wrong with the main plan; a recourse.

    โ€œAs a fallback, I suppose we can use typewriters if the word processing system fails.โ€

  3. 3

    A reduction in bitumen softening point, sometimes called refluxing or overheating in a relatively closed container.

  4. 4

    Pulverised material that falls back to earth after a nuclear explosion; fallout.

Source: https://en.wiktionary.org/wiki/fall-back, https://en.wiktionary.org/wiki/fallback