The Collaborative International Dictionary of English v.0.48:

hassle \hassle\ n.
   1. An inconvenience caused by difficulties encountered trying
      to accomplish a task; as, finding a parking place in
      midtown is always a hassle.

   Syn: fuss, trouble, bother.
        [WordNet 1.5]

   2. disorderly fighting; an angry dispute or disturbance.
      [WordNet sense 2]

   Syn: hassle, scuffle, tussle, rough-and-tumble.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

hassle \hassle\ v. i.
   1. to dispute or quarrel, often over petty disagreements.
      [PJC]

   2. To expend excessive time and energy trying to accomplish a
      task.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

hassle \hassle\ v. t.
   to repeatedly annoy; as, He is known to hassle his staff when
   he is overworked.

   Syn: harass, harry, chivy, chivvy, chevy, chevvy, beset,
        plague, molest, provoke.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

hassle
    n 1: an angry disturbance; "he didn't want to make a fuss";
         "they had labor trouble"; "a spot of bother" [syn: fuss,
         trouble, bother, hassle]
    2: disorderly fighting [syn: hassle, scuffle, tussle,
       dogfight, rough-and-tumble]
    v 1: annoy continually or chronically; "He is known to harry his
         staff when he is overworked"; "This man harasses his female
         co-workers" [syn: harass, hassle, harry, chivy,
         chivvy, chevy, chevvy, beset, plague, molest,
         provoke]

Moby Thesaurus II by Grady Ward, 1.0:

143 Moby Thesaurus words for "hassle":
   ado, agonize, altercation, anarchy, apologetics, apologia, apology,
   argue, argufy, argument, argumentation, bandy words, barney,
   battle, beef, bicker, bickering, bother, brawl, broil, brouhaha,
   buffet, bug, bump heads, carp at, casuistry, cavil, chaos,
   choplogic, clamor, commotion, confusion, contend, contention,
   contest, controversy, cross swords, cut and thrust, defense,
   discept, disputation, dispute, disturbance, donnybrook,
   donnybrook fair, dustup, embroilment, endeavor, essay,
   fabulous formless darkness, fight, flyting, foofaraw, foul-up,
   fracas, free-for-all, fret at, fuss, fuss at, give and take,
   grunt and sweat, have it out, helter-skelter, henpeck, hubbub,
   huff and puff, hurly-burly, join issue, knock-down-and-drag-out,
   license, litigation, lock horns, logomachize, logomachy,
   make a row, melee, miff, misrule, mix-up, moot, morass, muddle,
   nag, nibble at, niggle, paper war, passage of arms, peck at,
   pell-mell, pester, pettifog, pick at, pick on, plead, polemic,
   polemicize, polemics, polemize, pother, quibble, racket, rampage,
   rhubarb, riot, rough-and-tumble, roughhouse, row, ruckus, ruction,
   rumpus, run-in, scramble, scrap, screw-up, scuffle, set-to, shindy,
   snafu, spar, squabble, stir, strive, striving, struggle,
   take sides, thrash out, to-do, trial, trouble, try,
   try conclusions, tumult, turmoil, tussle, undertaking, uproar,
   verbal engagement, war of words, whirl, wrangle, wrangling,
   wrestle, yap at