The Collaborative International Dictionary of English v.0.48:

Dog \Dog\, v. t. [imp. & p. p. Dogged; p. pr. & vb. n.
   Dogging.]
   To hunt or track like a hound; to follow insidiously or
   indefatigably; to chase with a dog or dogs; to worry, as if
   by dogs; to hound with importunity.
   [1913 Webster]

         I have been pursued, dogged, and waylaid. -- Pope.
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         Your sins will dog you, pursue you.      --Burroughs.
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         Eager ill-bred petitioners, who do not so properly
         supplicate as hunt the person whom they address to,
         dogging him from place to place, till they even extort
         an answer to their rude requests.        -- South.
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The Collaborative International Dictionary of English v.0.48:

Dogged \Dog"ged\, a. [Fron. Dog.]
   1. Sullen; morose. [Obs. or R.]
      [1913 Webster]

            The sulky spite of a temper naturally dogged. -- Sir
                                                  W. Scott.
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   2. Sullenly obstinate; obstinately determined or persistent;
      as, dogged resolution; dogged work; dogged pursuit.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dogged
    adj 1: stubbornly unyielding; "dogged persistence"; "dour
           determination"; "the most vocal and pertinacious of all
           the critics"; "a mind not gifted to discover truth but
           tenacious to hold it"- T.S.Eliot; "men tenacious of
           opinion" [syn: dogged, dour, persistent,
           pertinacious, tenacious, unyielding]

Moby Thesaurus II by Grady Ward, 1.0:

125 Moby Thesaurus words for "dogged":
   adamant, assiduous, badgered, baited, balking, balky, bedeviled,
   beset, bigoted, bugged, bulldogged, bulletheaded, bullheaded,
   bullyragged, case-hardened, chivied, constant, continuing, deviled,
   diligent, dogmatic, enduring, faithful, fanatic, fretted, harassed,
   hardheaded, harried, haunted, headstrong, heckled, hectored,
   hounded, immutable, inalterable, indefatigable, indomitable,
   industrious, inexorable, insistent, intolerant, invincible,
   lasting, loyal, mulish, needled, never-tiring, nipped at, obdurate,
   obstinate, opinionated, overzealous, patient, patient as Job,
   permanent, persecuted, perseverant, persevering, persistent,
   persisting, pertinacious, pestered, picked on, pigheaded, plagued,
   plodding, plugging, preoccupied, ragged, rapt, relentless,
   resolute, restive, rigid, sedulous, self-willed, set,
   single-minded, sleepless, slogging, stable, steadfast, steady,
   stiff-necked, strong-willed, strongheaded, stubborn, sulky, sullen,
   teased, tenacious, tireless, tormented, unabating, unbending,
   unconquerable, uncooperative, undaunted, undiscouraged, undrooping,
   unfailing, unfaltering, unflagging, unflinching, unintermitting,
   uninterrupted, unnodding, unregenerate, unrelaxing, unrelenting,
   unremitting, unsleeping, unswerving, untiring, unwavering,
   unwearied, unwearying, unwinking, utterly attentive, vexed,
   weariless, willful, worried, worried sick, worried stiff