Definition of "fail"
fail1
/feɪl/
verb
third-person singular simple present fails, present participle failing, simple past and past participle failed
(intransitive) To be unsuccessful.
(transitive) To be wanting to, to be insufficient for, to disappoint, to desert; to disappoint one's expectations.
noun
countable and uncountable, plural fails
(uncountable, slang) Poor quality; substandard workmanship.
adjective
comparative more fail, superlative most fail
(slang, US) Unsuccessful; inadequate; unacceptable in some way.