Melancholic describes sadness, or a person who feels this way. Planning to go out dancing after seeing that melancholic movie? Don't be surprised if you feel more like sitting quietly, thinking, instead.
Melancholic means thoughtfully sad — your summer could be melancholic if you spent the whole season feeling blue, or you might have a melancholic friend who seems sad even when he swears he's having a good time. The Greek root melankholia means sadness, but it also means black bile, a bodily secretion believed in Medieval physiology to cause people to feel melancholic.