The word "microminiature" refers to something that is extremely small or tiny. Therefore, its antonyms or opposite words would be those that describe things on the opposite end of the size spectrum. Some possible antonyms for "microminiature" could be colossal, gigantic, enormous, or mammoth. Other antonyms might include words like huge, vast, or bulky, all of which have connotations of largeness, immensity, and size. It is important to note that choosing the right antonym will depend on the context in which the word is used, as the appropriate antonym will vary depending on the situation.