The term un-ceremonious means casual, informal, or disrespectful. However, there are several antonyms that suggest opposites of this word. For instance, the term formal means traditional, orthodox, or ceremonial, which is the exact opposite of un-ceremonious. Another antonym is ceremonious, which means solemn, dignified, or respectful. The term courteous can also be used as an antonym for un-ceremonious, as it suggests politeness, mannerliness, or graciousness. Other antonyms for un-ceremonious include respectful, punctilious, deferential, and decorous. Each of these words suggests a sense of structure, formality, or respect, which is the opposite of the informal and disrespectful tone of un-ceremonious.