Definition of: fail

(fāl) v.i.
1. To be unsuccessful; be unable.
2. To be deficient or wanting, as in ability, faithfulness, etc.; prove disappointing: He failed in his duty.
3. To give out: His strength failed.
4. To become extinct; die out.
5. To fade away; disappear: The light failed rapidly.
6. To weaken gradually, as in illness or death.
7. To become insolvent; go bankrupt.
8. To receive a failing grade.
—v.t.
9. To prove to be inadequate or of no help to; abandon; forsake: My courage fails me.
10. To leave undone or unfulfilled; neglect: with infinitive as object: He failed to carry out orders.
11. In education: a To receive a failing grade in (a course or test). b To assign a failing grade to (a pupil). See synonyms under FALL, SUSPEND.
—noun Failure: in the phrase without fail. [<OF faillir <L fallere to deceive]