"Frown on" is a phrase that means to disapprove of something strongly. There are many synonyms for this phrase, including "look down upon," "condemn," "disparage," "object to," "prohibit," "scorn," and "reject." All of these words convey a negative judgment towards a particular action or behavior and indicate an unwillingness to accept or tolerate that behavior. These synonyms for "frown on" can be useful in a variety of contexts, whether it's in a professional setting or in a personal relationship. By using these synonyms, you can communicate your strong disapproval of something and make it clear that certain behaviors will not be tolerated.