NOUN (1)

1. a bitter quarrel between two parties;


VERB (1)

1. carry out a feud;
- Example: "The two professors have been feuding for years"

The Collaborative International Dictionary of English v.0.48:

Feud \Feud\, n. [LL. feudum, feodum prob. of same origin as E.
   fief. See Fief, Fee.] (Law)
   A stipendiary estate in land, held of a superior, by service;
   the right which a vassal or tenant had to the lands or other
   immovable thing of his lord, to use the same and take the
   profits thereof hereditarily, rendering to his superior such
   duties and services as belong to military tenure, etc., the
   property of the soil always remaining in the lord or
   superior; a fief; a fee.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Feud \Feud\ (f[=u]d), n. [OE. feide, AS. f[=ae]h[eth], fr.
   f[=a]h hostile; akin to OHG. f[=e]hida, G. fehde, Sw. fejd,
   D. feide; prob. akin to E. fiend. See Foe.]
   1. A combination of kindred to avenge injuries or affronts,
      done or offered to any of their blood, on the offender and
      all his race.
      [1913 Webster]

   2. A contention or quarrel; especially, an inveterate strife
      between families, clans, or parties; deadly hatred;
      contention satisfied only by bloodshed.
      [1913 Webster]

            Mutual feuds and battles betwixt their several
            tribes and kindreds.                  --Purchas.

   Syn: Affray; fray; broil; contest; dispute; strife.
        [1913 Webster]

WordNet (r) 3.0 (2006):

feud
    n 1: a bitter quarrel between two parties
    v 1: carry out a feud; "The two professors have been feuding for
         years"

Moby Thesaurus II by Grady Ward, 1.0:

196 Moby Thesaurus words for "feud":
   acrimony, adverse possession, alodium, altercate, altercation,
   animosity, animus, antagonism, argument, avengement, bad blood,
   battle, bicker, bickering, bitter feeling, bitterness, blood feud,
   box, brawl, broil, burgage, claim, clash, close, collide, colony,
   combat, come to blows, conflict, contend, contention, contest,
   controversy, copyhold, cut and thrust, de facto, de jure,
   dependency, derivative title, differ, disagree, disagreement,
   discord, dispute, dissension, donnybrook, donnybrook fair, duel,
   embroilment, enmity, equitable estate, estate at sufferance,
   estate for life, estate for years, estate in expectancy,
   estate in fee, estate in possession, estate tail, estrangement,
   exchange blows, fall out, falling-out, fee, fee fief, fee position,
   fee simple, fee simple absolute, fee simple conditional,
   fee simple defeasible, fee simple determinable, fee tail, fence,
   feod, feodum, feudal estate, fief, fiefdom, fight, fight a duel,
   flite, fliting, fracas, frankalmoign, free socage, freehold, fuss,
   gavelkind, getting even, give and take, give satisfaction, grapple,
   grapple with, grudge, hard feelings, hatred, have words,
   having title to, hold, holding, hostility, ill blood, ill feeling,
   ill will, imbroglio, join issue, jostle, joust, knight service,
   lay fee, lease, leasehold, legal claim, legal estate,
   legal possession, logomachy, mandate, mix it up, occupancy,
   occupation, open quarrel, original title, owning, paramount estate,
   particular estate, polemic, possessing, possession, preoccupancy,
   preoccupation, prepossession, prescription, property,
   property rights, proprietary rights, quarrel, rancor, rassle,
   remainder, reprisal, retaliation, revanche, revanchism, revenge,
   reversion, riot, rivalry, row, run a tilt, run-in, scramble,
   scuffle, seisin, set to, sharp words, skirmish, slanging match,
   snarl, socage, soreness, sourness, spar, spat, squabble, squatting,
   strife, strive, struggle, sublease, sweet revenge, tenancy,
   tenantry, tenure, tenure in chivalry, thrust and parry, tiff, tilt,
   title, tourney, tussle, underlease, undertenancy, usucapion,
   vendetta, vengeance, venom, vested estate, villein socage,
   villeinhold, villenage, virulence, vitriol, wage war, war, words,
   wrangle, wrestle



Bouvier's Law Dictionary, Revised 6th Ed (1856):

FEUD. This word, in Scotland, signifies a combination of kindred to revenge
injuries or affronts done to any of their blood. Vide Fief.