feeling angry and unhappy because you feel that you have been treated unfairly 愤愤不平的She is very bitter about losing her job.她丢掉了工作，心里很不服气。
used about a determined and angry enemy or opponent （敌人或对手）势不两立的，怀恨的
one of the President’ s most bitter critics
对总统态度最激烈的批评者之一
They had always been bitter rivals.
他们一直是势不两立的竞争对手。