sour in WordNet English dictionary

1. make sour or more sour
   sour  acidify  acidulate  acetify 
   
2. go sour or spoil
   "The milk has soured"; "The wine worked"; "The cream has turned--we have to throw it out"
   sour  turn  ferment  work 
   

1. the property of being acidic
   sourness  sour  acidity 
   
2. the taste experience when vinegar or lemon juice is taken into the mouth
   sour  sourness  tartness 
   
3. a cocktail made of a liquor (especially whiskey or gin) mixed with lemon or lime juice and sugar
   sour 
   

1. 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"
   dark  dour  glowering  glum  moody  morose  saturnine  sour  sullen 
   
2. inaccurate in pitch
   "a false (or sour) note"; "her singing was off key"
   false  off-key  sour 
   
3. in an unpalatable state
   "sour milk"
   off  sour  turned 
   
4. smelling of fermentation or staleness
   sour  rancid 
   
5. having a sharp biting taste
   sour 
   
6. one of the four basic taste sensations; like the taste of vinegar or lemons
   sour