Unfog means to clear or clarify something that is clouded or obscured. Its antonyms, therefore, would refer to things that cause cloudiness or obscurity. Some possible antonyms for unfog could be words like fogging, obscuring, clouding, muddling, confusing, veiling, or blurring. For instance, one might say that mist or smoke can fog up a windshield, or that a dense fog can obscure a street sign. Similarly, a muddy river might blur the reflection of the sky above it, or the complexity of a scientific theory might confuse a layperson attempting to understand it. All of these things could be considered antonyms of the verb unfog.