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1. A feeling of deep and bitter anger and ill-will
   "his bitterness took the form of extreme hostility";
   - resentment, gall, rancor [US], rancour [Brit, Cdn], ill feeling, hard feelings, acrimoniousness, bile
    
2. A rough and bitter manner
   - acrimony, acerbity, jaundice, tartness, thorniness
    
3. The taste experience when quinine or coffee is taken into the mouth
   - bitter
    
4. The property of having a harsh unpleasant taste
   - bitter

Type of: disagreeableness, enmity, gustatory perception, gustatory sensation, hostility, ill will, taste, taste perception, taste property, taste sensation

Encyclopedia: Bitterness