(archaic) third-person singular simple present indicative form of fall

An act of falling back. / A backup plan or contingency strategy; an alternative which can be used if something goes wrong with the main plan; a recourse.

That can be resorted to as a fallback.

Misspelling of fall back.

material settling from a radioactive plume, and its subsequent surface deposition

plural of Fallopian tube

(logic) argumentum ad populum.

plural of fallacy

A fallacy; a clearly defined error in reasoning used to support or refute an argument, excluding simple unintended mistakes. / A formal fallacy.

A thick-walled building, usually under the ground, built so that people can keep away from dust after a nuclear explosion.