Self-annulling is a term used to describe something that negates or cancels itself out. There are many different words that can be used as synonyms for self-annulling, including self-contradictory, self-defeating, self-destructive, self-sabotaging, and self-undermining. Each of these words describes something that is ultimately harmful to itself because of its own actions or characteristics. For example, a self-contradictory statement is one that contradicts itself, making it impossible to believe or follow. Self-destructive behaviors are actions that harm the person engaging in them, and self-sabotaging behaviors are actions that undermine one's own success or progress. In all cases, the key idea is that something is working against itself, ultimately leading to its downfall.