DECO'RUM, noun [Latin to become.] 1. Propriety of speech or behavior; suitableness of speech and behavior, to one's own character, and to the characters present, or to the place and occasion; seemliness; decency; opposed to rudeness, licentiousness, or levity. To speak and behave with decorum is essential to good breeding. 2. In architecture, the suitableness of a building, and of its parts and ornaments, to its place and uses.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI