The word "canceler" refers to a person or thing that cancels or nullifies something. Synonyms for this word include "annuller," "repealer," "rescinder," "reverser," "voider," "undoer," "abolisher," and "invalidator." These synonyms can all be used interchangeably with "canceler" in many contexts. For instance, someone who voids a contract could be called a "contract canceler" or an "invalidator." Similarly, a law or policy that is repealed might be referred to as "cancelled" or "cancelled out." In any case, using these synonyms can help to add variety and color to your language, while still conveying the same basic meaning.