"Quadrigamist" refers to a person who is married four times. Synonyms for this term are not common as it is a specific and unusual condition. However, some words that could be used to describe a person who has been married multiple times include serial monogamist, polygamist, or just simply someone who has had four marriages. Other words that could be used to describe a person's marital status include "four-times married" or "four-time spouse." In any case, the term "quadrigamist" is a very specific indicator of a person's marital history and is not often used in everyday language.