Subreptitious is an adjective that is used to describe actions or behavior that are secretive, stealthy, or sly. When trying to describe something as subreptitious, one might also use words like clandestine, covert, furtive, or surreptitious. Other synonyms could include sneaky, hidden, underhanded, or devious. These words can be used interchangeably depending on the context and tone of the sentence. It's important to choose the right synonym to convey the appropriate meaning in any given situation. Overall, subreptitious is a powerful word that can add significant nuance and depth to any written or spoken communication.