Swears down is a phrase commonly used to express an adamant assertion or affirmation. The word "swears" refers to the act of making a solemn promise or declaration, while "down" emphasizes the seriousness and sincerity of the assertion. Antonyms for swears down include terms like refutes, denies, contradicts, and challenges. These words indicate the opposite meaning of a statement, suggesting that it is untrue or incorrect. Other antonyms that could be used in this context include disavows, rejects, repudiates, and disputes. These terms can be helpful for adding nuance and complexity to language, allowing speakers to convey a range of different ideas and emotions.