"Go batty" is a colloquial phrase that means to become crazy or lose one's mind. There are several synonyms that can be used instead of "go batty," such as "go crazy," "lose it," "go mental," "lose your marbles," or "go bonkers." Each of these phrases conveys a similar meaning to "go batty" and can be used in place of it depending on the context. It's important to recognize that these phrases are informal and should not be used in more formal settings. When used in informal settings, these synonyms can add humor and color to everyday conversation.