Extramarital affair is a common term used to describe infidelity in a marriage or committed relationship, but there are many synonyms one can use to describe the same thing. Some other phrases or words that are often used to describe an extramarital affair include cheating, adultery, unfaithfulness, indiscretion, liaison, affair, fling, tryst, affair of the heart, affair of honor, violation of trust, breach of commitment, and disloyalty. These synonyms can help to better describe the situation at hand, and give a more nuanced understanding of what is happening in a relationship where one partner has been unfaithful.