Antonyms for costume balls include casual gatherings, impromptu hangouts, plain clothes picnics, or even formal events. Unlike costume balls, casual gatherings are spontaneous and do not usually require much planning or effort. Impromptu hangouts are unplanned and can occur at any time, while plain clothes picnics require the attendees to wear everyday civilian clothes. Formal events, on the other hand, require guests to dress up in elegant attire but not in specific costumes. While costume balls may be exciting, antonyms offer a more relaxed and unrestricted atmosphere for socializing without the hassle of finding and wearing elaborate costumes.