"Mopey" is a word that describes someone who is sad, sullen, and lacking in energy or enthusiasm. Some synonyms for "mopey" include despondent, gloomy, morose, dejected, and depressed. Other similar words might include melancholy, forlorn, crestfallen, disheartened, and desolate. These words all convey a sense of sadness or despair, but each has its own unique shade of meaning. For example, someone who is "despondent" might feel like giving up entirely, while someone who is "dejected" might feel disheartened as a result of a recent disappointment. Ultimately, all of these words serve to describe someone who is experiencing a low mood or emotional funk.