What is the meaning of sour?

noun

• A cocktail made of a liquor (especially whiskey or gin) mixed with lemon or lime juice and sugar.
• The taste experience when vinegar or lemon juice is taken into the mouth.
  • synonyms: sourness, tartness
• The property of being acidic.
  • synonyms: sourness, acidity

verb

• Go sour or spoil.
  • usage: "The milk has soured"; "The wine worked"; "The cream has turned-we have to throw it out"
  • synonyms: turn, ferment, work
• Make sour or more sour.
  • synonyms: acidify, acidulate, acetify

adjective

• Smelling of fermentation or staleness.
  • synonyms: rancid
• Having a sharp biting taste.
• One of the four basic taste sensations; like the taste of vinegar or lemons.
• In an unpalatable state.
  • usage: "sour milk"
  • synonyms: off, turned
• Inaccurate in pitch.
  • usage: "a false (or sour) note"; "her singing was off key"
  • synonyms: false, off-key
• Showing a brooding ill humor.
  • usage: "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"
  • synonyms: dark, dour, glowering, glum, moody, morose, saturnine, sullen