Sadsack is a colloquial term used to describe someone who is constantly unhappy or miserable. This can be due to a variety of reasons, such as personal issues, work-related stress or relationship problems. However, there are a number of synonyms for this word that can be used to describe someone who is feeling down or depressed. These include words such as melancholy, despondent, dejected, crestfallen, downcast, disheartened, and saddened. Each of these words helps to capture the feeling of sadness and can be used interchangeably with sadsack in order to describe someone who is struggling with their emotions.