fallback

Short definition from Wiktionary

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.
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.

Adjective

1. 1
   That can be resorted to as a fallback.

Verb

1. 1
   Misspelling of fall back.