n. Lack of decorum; impropriety of behavior; violation of the accepted rules of conduct.n. An indecorous or unbecoming act; a breach of decorum.n. Synonyms Indecorum, Indelicacy, Indecency. An indecorum violates a rule or rules of civility or order: as, it is an indecorum to interrupt a speaker in debate; an indelicacy and an indecency are a low and a high degree of violation of the rules of modesty: as, there would be a manifest indelicacy, not to say indecency, in his putting himself forward for a public office; indelicacies or indecencies in speech or action. Indecency is used rather freely for anything shameful in conduct.