v. failed, fail·ing, fails
1. To prove deficient or lacking; perform ineffectively or inadequately: failed to fulfill their promises; failed in their attempt to reach the summit.
a. To be unsuccessful: an experiment that failed.
b. To be unsuccessful in being acted upon: an idea that failed to be accepted by the board.
3. To receive an academic grade below the acceptable minimum.
4. To prove insufficient in quantity or duration; give out: The water supply failed during the drought.
5. To decline, as in strength or effectiveness: The light began to fail.
6. To cease functioning properly: The engine failed.
7. To give way or be made otherwise useless as a result of excessive strain: The rusted girders failed and caused the bridge to collapse.
8. To become bankrupt or insolvent: Their business failed during the last recession.
1. To disappoint or prove undependable to: Our sentries failed us.
2. To abandon; forsake: His strength failed him.
3. To omit to perform (an expected duty, for example): We must not fail our obligation to the earthquake victims.
4. To leave undone; neglect: failed to wash the dishes.
a. To receive an academic grade below the acceptable minimum in (a course, for example): failed algebra twice.
b. To give such a grade of failure to (a student): failed me in algebra.
6. To be detected by (a drug test) as having used a banned substance.
1. A failing grade: The student received a fail on the final paper.
2. Informal Something that does not achieve the desired result; a failure: My first attempt to make flourless cookies was a big fail.
1. With no chance of failure: Be here at noon without fail.
2. Every single time: "Always we get a good rain on Labor Day, without fail—like clockwork" (Rick Bass)."Whenever he returned to his hut, almost without fail some money was missing from the basket" (Paul Theroux).
[Middle English failen, from Old French faillir, from Vulgar Latin *fallīre, variant of Latin fallere, to deceive.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.