The phrase "poorly dressed" typically describes someone who lacks style or fashion sense. However, there are many synonyms that can be used to describe someone's inadequate choice of attire. Some of these synonyms include sloppily dressed, shabbily dressed, unprofessionally dressed, unkempt, and disheveled. You could also describe someone as dressed inappropriately, drably, or simply as having a bad sense of fashion. Ultimately, the words you choose to use will depend on the context and severity of the poor dressing. Nevertheless, there are plenty of ways to describe someone who is not presenting themselves well through their clothing choices.