The term "out of keeping" means that something is not in harmony or out of sync with its surroundings. Its antonyms would include words like "appropriate," "suitable," "harmonious," "matching," "compatible," and "consistent." When something is appropriate, it fits well with its environment and does not stand out in a negative way. Similarly, when something is harmonious, it blends in with its surroundings and feels natural. Likewise, when something is compatible, it fits well with other things around it and works well within a system. By using the antonyms of "out of keeping," one can better convey a sense of harmony and balance in their writing or speech.