bitter or scornful
"the face was saturnine and swarthy, and the sensual lips...twisted with disdain"
showing a brooding ill humor
"a dark scowl"
"the proverbially dour New England Puritan"
"a glum, hopeless shrug"
"he sat in moody silence"
"a morose and unsociable manner"
"a saturnine, almost misanthropic young genius"
"a sour temper"
"a sullen crowd"
Of a person: having a tendency to be cold, bitter, gloomy, sarcastic, and slow to change and react.