Being diffuse refers to the quality of being unclear or lacking focus, and is typically an undesirable trait in communication or writing. Antonyms for being diffuse would include adjectives such as concise, precise, focused, and succinct. These words describe the opposite of being diffuse, with a clear, direct and well-defined approach to communication. Other potential antonyms might include terms such as specific, brief, or to the point, all of which suggest a level of clarity and intentionality that stands in stark contrast to communication or writing that is diffuse, unfocused, or imprecise. Ultimately, choosing the right words to communicate effectively requires careful consideration of meaning and context, as well as the desired impact among your intended audience.