Haddest a fling is a common phrase used to describe a brief romantic encounter or a casual relationship. However, there are various synonyms that can be used to describe this type of relationship. Some alternatives include having a one-night stand, engaging in a short-lived affair, or having a casual liaison. Other related terms could be using the phrase "hooking up" or "having a casual tryst." It's critical to note that while these phrases may have similar meanings, they can also imply different connotations and levels of intensity in the relationship. Ultimately, it's essential to choose the language that best matches the context and tone of the situation.