The word "un customary" refers to something that is not customary or usual. Its opposite, or antonym, is "customary." Something that is customary is typical or normal for a particular situation or circumstance. For example, it is customary to shake hands when you meet someone for the first time. Other antonyms for "un customary" include common, typical, regular, standard, and habitual. These words all refer to something that is customary or usual. Antonyms help us to understand the meaning of a word by giving us a point of comparison. In this case, the antonyms for "un customary" help us to understand what is typical or expected.