Unnatural act is an expression that refers to behaviors or actions that are considered abnormal or not conforming to societal norms. There are several synonyms that can be used in place of unnatural act, including deviant behavior, abnormal behavior, perverse act, aberrant behavior, or abnormal conduct. These terms describe behaviors that deviate from accepted social norms, morals, or values. These words are often used in legal contexts to describe criminal or immoral behavior, as well as in everyday conversations to describe actions that are considered distasteful or unacceptable. It is important to note that using these words can be stigmatizing and judgmental, so it is best to use them with care and sensitivity.