The word "un decorous" typically refers to behaviour or actions that are inappropriate, rude, or disrespectful in social situations. Some antonyms for "un decorous" include "proper," "appropriate," "polite," "respectful," "courteous," "refined," and "dignified." These words describe actions and attitudes that are expected and accepted within a particular social or cultural context. Acting in a decorous manner shows consideration and sensitivity towards other people's feelings and expectations, which is vital to maintain good relationships and avoid offending others. Thus, when describing a behaviour or action that is opposite to "un decorous," it is wise to use words that convey a sense of etiquette, cultural norms, and respect.