The opposite of "wast certain of" can be "doubtful" or "unsure." When someone is doubtful, they lack confidence or trust in the information or situation. Doubtfulness can stem from skepticism, uncertainty, or skepticism. In contrast, when someone is wast certain of something, they are confident that it is true or will happen. Other antonyms for wast certain of could include "ambivalent," "hesitant," "indecisive," "disbelieving," or "questioning." These words all indicate a lack of conviction or certainty in a particular issue, idea, or piece of information. Understanding antonyms like these helps us to more fully grasp the nuances of language and better express our thoughts and emotions.