Atrabiliar is a rarely used word that refers to a disposition that is irritable, melancholy or prone to gloom. Some synonyms for atrabiliar include morose, sulky, sullen, glum, gloomy, irritable, ill-humoured, moody, cranky, and sour. All of these words describe a negative mood or disposition that is associated with sadness, frustration or irritability. While not widely used today, it's still a useful and relevant word for those looking to describe a certain temperament or mood. Whether in literature, poetry or everyday speech, having a range of synonyms for words like atrabiliar ensures that we can remain expressive and versatile in our language.