The phrase "two-time" generally means to deceive or betray someone by having a secret relationship or engagement with another person. There are numerous synonyms that can be used to express this concept, including deceive, cheat, betray, trick, mislead, backstab, or double-cross. These words highlight the sense of betrayal and dishonesty that comes with "two-timing" someone. Other related terms might include infidelity, adultery, unfaithfulness, disloyalty, or breach of trust. Whether used in personal relationships, business dealings, or other contexts, these terms convey a sense of betrayal and hurt that accompanies such unscrupulous behavior.