Playing up is a common expression used to describe someone who is misbehaving or causing trouble. However, there are several other synonyms that can be used to convey the same meaning. These include acting out, being disobedient, causing a nuisance, creating a disturbance, making mischief, stirring up trouble, throwing a tantrum, and wreaking havoc. Each of these synonyms can be used in different situations, depending on the context and level of misbehavior. Regardless of the word chosen, it is important to address the behavior and take appropriate steps to correct it, whether through discipline or communication.