From WordNet (r) 3.0 (2006):
sour
adj 1: smelling of fermentation or staleness [syn: sour,
rancid]
2: having a sharp biting taste [ant: sweet]
3: one of the four basic taste sensations; like the taste of
vinegar or lemons
4: in an unpalatable state; "sour milk" [syn: off, sour,
turned]
5: inaccurate in pitch; "a false (or sour) note"; "her singing
was off key" [syn: false, off-key, sour]
6: 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"-
Bruce Bliven; "a sour temper"; "a sullen crowd" [syn: dark,
dour, glowering, glum, moody, morose, saturnine,
sour, sullen]
n 1: a cocktail made of a liquor (especially whiskey or gin)
mixed with lemon or lime juice and sugar
2: the taste experience when vinegar or lemon juice is taken
into the mouth [syn: sour, sourness, tartness]
3: the property of being acidic [syn: sourness, sour,
acidity]
v 1: go sour or spoil; "The milk has soured"; "The wine worked";
"The cream has turned--we have to throw it out" [syn:
sour, turn, ferment, work]
2: make sour or more sour [syn: sour, acidify, acidulate,
acetify] [ant: dulcify, dulcorate, edulcorate,
sweeten]