sour
Pronunciation: /saʊə/
adjective
- 1having an acid taste like lemon or vinegar: she sampled the wine and found it was sour
- (of food, especially milk) having gone bad because of fermentation: the kitchen smelled of sour milk
- having a rancid smell: her breath was always sour
verb

Phrases
-
go (or turn) sour
- become less pleasant; turn out badly: their relationship began to turn sour
-
sour grapes
- used to refer to an attitude in which someone adopts a negative attitude to something because they cannot have it themselves: government officials dismissed many of the complaints as sour grapes[with allusion to Aesop's fable The Fox and the Grapes]

Origin:
Old English sūr, of Germanic origin; related to Dutch zuur and German sauer