The Collaborative International Dictionary of English v.0.48:

Harassment \Har"ass*ment\ (-ment), n.
   The act of harassing, or state of being harassed; worry;
   annoyance; anxiety.
   [1913 Webster]

         Little harassments which I am led to suspect do
         occasionally molest the most fortunate.  --Ld. Lytton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

harassment
    n 1: a feeling of intense annoyance caused by being tormented;
         "so great was his harassment that he wanted to destroy his
         tormentors" [syn: harassment, torment]
    2: the act of tormenting by continued persistent attacks and
       criticism [syn: harassment, molestation]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "harassment":
   McCarthyism, aggravation, annoyance, annoyingness, bad news,
   bedevilment, bore, bother, botheration, bothering, bothersomeness,
   crashing bore, devilment, difficulty, disturbance, dogging, downer,
   drag, exasperation, fretting, harrying, headache, hounding, irking,
   irksomeness, irritation, molestation, nuisance, oppression,
   persecution, perturbation, peskiness, pest, pestiferousness,
   plaguesomeness, problem, provocation, provoking, provokingness,
   red-baiting, tiresomeness, torment, tormenting, trial, trouble,
   troublesomeness, vexation, vexatiousness, vexing, victimization,
   wearisomeness, witch-hunt, witch-hunting, worriedness,
   worries and cares, worriment, worrisomeness, worry, worrying