The phrase "having a whack" typically means trying or attempting something. It can also refer to striking someone or something. Some antonyms that could be used to describe the opposite of having a whack could be avoiding, neglecting, delaying, or disregarding. These words indicate that someone is not engaged in an activity, opposite of attempting something. Instead, they may be purposely avoiding it, showing disinterest or focusing on other things. Additionally, antonyms like calming, relaxing, soothing, or pacifying can indicate that someone is intentionally taking a break, opposite of striking or attempting something.