The word "tergiversate" means to change sides or to be evasive in order to avoid stating one's position. Antonyms for this word would include terms such as stand firm, remain loyal, be forthright, or maintain one's stance. Other antonyms could include negotiate, collaborate, compromise, or find common ground. These words imply an openness to discussion and a willingness to work towards a consensus rather than simply switching sides or avoiding a clear declaration of opinion. Ultimately, the choice of antonym depends on the context in which the word "tergiversate" is being used, but any of these options would provide a clear contrast to the notion of wavering or being noncommittal.