Adulter is a word that refers to someone who engages in extramarital affairs or cheats on their partner. There are many other words that can be used as synonyms for this term, including philanderer, cheat, unfaithful, faithless, two-timer, and player. Each of these words has somewhat different connotations that can be used to paint a more detailed picture of the person in question. For example, a philanderer might be seen as someone who is always chasing after new conquests, while a cheat may be viewed as someone who lies and deceives in order to maintain their infidelity. Ultimately, the choice of synonym will depend on the context and intended meaning.