bitterness

noun

The quality or state of feeling bitter: acrimony, embitterment, gall, rancor, rancorousness, resentfulness, resentment, virulence, virulency. See feelings.

The noun has 4 meanings:

Meaning #1: a feeling of deep and bitter anger and ill-will
  Synonyms: resentment, gall, rancor, rancour

Meaning #2: a sharp and bitter manner
  Synonyms: acrimony, acerbity, jaundice

Meaning #3: the taste experience when quinine or coffee is taken into the mouth
  Synonym: bitter

Meaning #4: the property of having a harsh unpleasant taste
  Synonym: bitter