Acting cool is a term that is often used to describe someone who is calm and composed in a situation. However, there are several antonyms for this phrase that can mean the opposite. For instance, one antonym for acting cool is "freaking out," which means to become highly anxious or agitated. Another antonym for acting cool is "losing one's cool," which means to become highly emotional, angry or upset. Some other antonyms for acting cool include "panicking," "stressing out," and "fidgeting." These words serve as a reminder that sometimes it's okay to let our emotions show and be genuine in how we respond to different situations.