When someone forswears themselves, they are essentially swearing falsely or making a false promise. It is a serious offense and can lead to a loss of trust or credibility. People may forswear themselves for a variety of reasons, including attempting to deceive others or avoiding responsibility. Synonyms for the word "forswears oneself" include perjure, deceive, mislead, lie, break faith, fail to keep a promise, renege, blaspheme, and commit perjury. It is important to maintain honesty and integrity in all interactions to build relationships and trust with others.