Most matter-of-course refers to something that is very common, usual, or expected. Its antonyms would be words that describe something that is uncommon, unusual, or not expected. Some antonyms for most matter-of-course could be rare, abnormal, extraordinary, irregular, or bizarre. These words describe something that is out of the ordinary and not normal. Most matter-of-course is a term used to describe something that is taken for granted, while its antonyms describe situations or events that are unexpected and require attention. Understanding antonyms for most matter-of-course can help expand your vocabulary and provide you with other ways of expressing yourself.