The Collaborative International Dictionary of English v.0.48:

Harass \Har"ass\ (h[a^]r"as or h[.a]*r[a^]s"), v. t. [imp. & p.
   p. Harassed (h[a^]r"ast or h[.a]*r[a^]st"); p. pr. & vb. n.
   Harassing.] [F. harasser; cf. OF. harace a basket made of
   cords, harace, harasse,a very heavy and large shield; or
   harer to set (a dog) on.]
   To fatigue; to tire with repeated and exhausting efforts;
   esp., to weary by importunity, teasing, or fretting; to cause
   to endure excessive burdens or anxieties; -- sometimes
   followed by out.
   [1913 Webster]

         [Troops] harassed with a long and wearisome march.
                                                  --Bacon.
   [1913 Webster]

         Nature oppressed and harass'd out with care. --Addison.
   [1913 Webster]

         Vext with lawyers and harass'd with debt. --Tennyson.

   Syn: To weary; jade; tire; perplex; distress; tease; worry;
        disquiet; chafe; gall; annoy; irritate; plague; vex;
        molest; trouble; disturb; torment.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Harass \Har"ass\, n.
   1. Devastation; waste. [Obs.] --Milton.
      [1913 Webster]

   2. Worry; harassment. [R.] --Byron.
      [1913 Webster]

WordNet (r) 3.0 (2006):

harass
    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]
    2: exhaust by attacking repeatedly; "harass the enemy"

Moby Thesaurus II by Grady Ward, 1.0:

191 Moby Thesaurus words for "harass":
   abuse, afflict, aggravate, aggrieve, ail, annoy, badger, bait,
   be at, be the matter, beat, bedevil, befoul, beleaguer, beset,
   besiege, bewitch, blight, blockade, bludgeon, bluster,
   bluster out of, bother, bristle, browbeat, brown off, bug,
   bulldoze, bully, bullyrag, burn out, burn up, chevy, chivy,
   complicate matters, concern, condemn, corrupt, cow, crucify, curse,
   damage, debilitate, defile, demoralize, deprave, despoil, destroy,
   devil, disadvantage, discommode, discompose, disserve, distemper,
   distress, disturb, do a mischief, do evil, do ill, do in, do up,
   do wrong, do wrong by, dog, doom, dragoon, encircle, encompass,
   enervate, envelop, envenom, exasperate, exercise, exhaust, fag,
   fag out, fash, fatigue, flag, foray, frazzle, fret, get,
   get into trouble, gnaw, gripe, harm, harry, haunt, heckle, hector,
   hex, hound, huff, hunt, hurt, impair, inconvenience, infect,
   injure, intimidate, invest, irk, irritate, jade, jinx, knock out,
   knock up, lay siege to, maltreat, maraud, menace, miff, mistreat,
   molest, nag, needle, nettle, nudzh, oppress, outrage, overfatigue,
   overstrain, overtire, overweary, pain, peeve, perplex, persecute,
   perturb, pester, pick at, pick on, pique, plague, play havoc with,
   play hob with, pluck the beard, poison, pollute, poop, poop out,
   pother, prejudice, prostrate, provoke, pursue, put out, put to it,
   puzzle, ride, rile, roil, ruffle, savage, scathe, soften up,
   strain, stress, surround, systematically terrorize, taint, tease,
   terrorize, threaten, tire, tire out, tire to death, torment,
   torture, trouble, try, try the patience, tucker, tweak the nose,
   use up, vex, victimize, violate, weaken, wear, wear down, wear on,
   wear out, weary, wilt, wind, worry, wound, wreak havoc on, wrong