Swingy, an adjective that describes something that moves or sways easily, can have several antonyms depending on the context. If used to describe a stiff or inflexible item, synonyms such as rigid, immobile, or still could be used as antonyms. Alternatively, for something that does not move at all, terms like stationary, motionless, or fixed could be used. However, if referring to a person's physical movements, the antonyms could be clumsy, awkward, or uncoordinated. Ultimately, the opposite of swingy will depend on the specific context in which it is used, and choosing the right antonym will help to create a clear and accurate meaning.