noun

a prolonged and bitter quarrel or dispute.

his long-standing feud with Universal Pictures

verb

be engaged in a prolonged and bitter quarrel or dispute.

Hoover feuded with the CIA for decades

quarrel,fight,argue,bicker,squabble,dispute,clash,differ,be at odds,be at daggers drawn,wage war,take up arms,scrap,fall out,go at it hammer and tongs,fight like cat and dog