The word "passe" can be defined as something that is outdated or no longer relevant. Synonyms for this word could include phrases such as outdated, old-fashioned, or obsolete. Other possible synonyms for "passe" could be terms like antiquated, behind the times, or fossilized. Additionally, one could use expressions such as out of style, outmoded, or passe to describe something as no longer fashionable or in vogue. Other synonyms might include archaic, dated, or defunct, all of which describe something that is no longer in use or relevant to current events. Overall, there are many words that can be used to describe something that is "passe," but all of them convey the same basic idea of being outdated or out of touch with the modern world.