Decorum means dignity of appropriateness of behavior.
Decorum is a noun.
Synonyms: tact, taste, good form, gentility, dignity, breeding, propriety, politeness.
Antonyms: inappropriate behavior, rudeness, bad manners, impropriety.
All decorum was set aside when the Minister went away for the weekend.
Please act with decorum at the next meeting and resist your tendency to make rude gestures.
The manager expects their workers to act with decorum; they must act with dignity and use good manners.
The decorous young boy from the finishing school showed a complete lack of decorum during summer break.