sour sour /ˈsaʊr/

adjective

1. () Smelling of fermentation or staleness  ( rancid , sour )
   smelling of fermentation or staleness
   
2. Showing a brooding ill humor  ( dark , dour , glum , glowering , moody , morose , saturnine , sour , sullen )
   showing a brooding ill humor
    A dark scowl
   a dark scowl
    The proverbially dour New England Puritan
   the proverbially dour New England Puritan
    A glum, hopeless shrug
   a glum, hopeless shrug
    He sat in moody silence
   he sat in moody silence
    A morose and unsociable manner
   a morose and unsociable manner
    A saturnine, almost misanthropic young genius
   a saturnine, almost misanthropic young genius
    A sour temper
   a sour temper
    A sullen crowd
   a sullen crowd
   
3. Inaccurate in pitch  ( false , off-key , sour )
   inaccurate in pitch
    A false (or sour) note
   a false (or sour) note
    Her singing was off key
   her singing was off key
   
4. Having a sharp biting taste  ( sour )
   having a sharp biting taste
    Lemons are sour and are often used in cooking and baking
   Lemons are sour and are often used in cooking and baking
   
5. In an unpalatable state  ( off , sour , turned )
   in an unpalatable state
    Sour milk
   sour milk
   
6. One of the four basic taste sensations; like the taste of vinegar or lemons  ( sour )
   one of the four basic taste sensations; like the taste of vinegar or lemons
   

noun

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

verb

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