Antiquation, meaning outdated or obsolete, can be replaced with several synonyms. Some of these synonyms include archaism, which means the use of old-fashioned language or styles. Another synonym is antiquatedness, which refers to the state of being old-fashioned or out of date. Obsolescence is also a synonym that describes something that is no longer in use or has become outdated. Moreover, the word anachronism is another synonym that describes something that is out of place, in terms of time. Overall, there are a number of words that can be used in place of antiquation depending on the context and situation.