Coact is a word that is not commonly used in daily language. However, there are a few synonyms that can replace the word if necessary. Collaborate, work together, cooperate, and join forces are some of the synonyms for the word coact. These words describe the act of two or more people working together to achieve a common goal. Use of different synonyms for coact will depend on the context of the sentence. For instance, "collaborate" will be more relevant when describing teamwork in a professional setting, while "join forces" signifies the act of working together towards a specific goal. Therefore, it is essential to choose the right synonym depending on the context of the sentence.