Mopier is an adjective that describes someone who feels sad or gloomy, often due to loneliness or a sense of disenchantment. Some synonyms for mopier include melancholic, dejected, dispirited, glum, somber, and despondent. These words all describe a similar emotional state of sadness or low energy, but may vary in intensity or root cause. Other related terms include crestfallen, blue, forlorn, and downcast. It's important to note that feeling sad or low at times is a normal part of the human experience, and seeking help or support from loved ones or a professional may be helpful for those struggling with these emotions.