feud

Short definition from Wiktionary

Noun

1. 1
   A state of long-standing mutual hostility.
2. 2
   A staged rivalry between wrestlers.
3. 3
   A combination of kindred to avenge injuries or affronts, done or offered to any of their blood, on the offender and all his race.
4. 4
   An estate granted to a vassal by a feudal lord in exchange for service.

Verb

1. 1
   To carry on a feud.