The word "dueler" refers to someone who engages in a duel. There are several synonyms or alternative words that can be used in place of "dueler". One common synonym is "duelist", which is perhaps the most common usage of the term. Other possible synonyms include "combatant", "challenger", "contestant", "opponent", or "protagonist". Depending on the context in which the word is used, there may be other options as well, such as "rival", "adversary", or "foe". Ultimately, the choice of synonym will depend on the specific nuances of the situation and the desired tone or emphasis.