Noun
(music) An incorrect note which is sung or played in a musical performance.
(idiomatic, by extension) In a remark or narrative, an indication (as discerned by the listener or reader) of untruth, insincerity, or inconsistency.
(idiomatic, by extension) In a non-verbal display or presentation, an indication of incongruity or inappropriateness.
Source: en.wiktionary.org