The Collaborative International Dictionary of English v.0.48:

Fag \Fag\, v. i. [imp. & p. p. Fagged (f[a^]gd); p. pr. & vb.
   n. Fagging (f[a^]g"g[i^]ng).] [Cf. LG. fakk wearied, weary,
   vaak slumber, drowsiness, OFries. fai, equiv. to f[=a]ch
   devoted to death, OS. f[=e]gi, OHG. feigi, G. feig, feige,
   cowardly, Icel. feigr fated to die, AS. f[=ae]ge, Scot. faik,
   to fail, stop, lower the price; or perh. the same word as E.
   flag to droop.]
   1. To become weary; to tire.
      [1913 Webster]

            Creighton withheld his force till the Italian began
            to fag.                               --G.
                                                  Mackenzie.
      [1913 Webster]

   2. To labor to wearness; to work hard; to drudge.
      [1913 Webster]

            Read, fag, and subdue this chapter.   --Coleridge.
      [1913 Webster]

   3. To act as a fag, or perform menial services or drudgery,
      for another, as in some English schools.
      [1913 Webster]

   To fag out, to become untwisted or frayed, as the end of a
      rope, or the edge of canvas.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

fagged \fagged\ adj.
   1. same as burned-out, 1.

   Syn: burned-out(prenominal), burnt-out(prenominal), burned
        out(predicate), burnt out(predicate), exhausted,
        fatigued, played-out(prenominal), played out(predicate),
        spent, washed-out(prenominal), washed out(predicate),
        worn-out(prenominal), worn out(predicate).
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

fagged
    adj 1: drained of energy or effectiveness; extremely tired;
           completely exhausted; "the day's shopping left her
           exhausted"; "he went to bed dog-tired"; "was fagged and
           sweaty"; "the trembling of his played out limbs"; "felt
           completely washed-out"; "only worn-out horses and
           cattle"; "you look worn out" [syn: exhausted, dog-
           tired, fagged, fatigued, played out, spent,
           washed-out, worn-out(a), worn out(p)]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "fagged":
   all in, beat, beat up, beaten, bone-weary, bushed, dead,
   dead-and-alive, dead-tired, deadbeat, debilitated, dog-tired,
   dog-weary, done, done in, done up, drained, drooping, droopy,
   enervated, enfeebled, exhausted, fagged out, faint, fainting,
   fatigued, feeling faint, flagging, footsore, frazzled, gone,
   good and tired, jaded, knocked out, languid, played out, pooped,
   pooped out, prostrate, ready to drop, run ragged, run-down,
   sagging, seedy, spent, tired, tired out, tired to death,
   tired-winged, toilworn, tuckered out, unrefreshed, unrestored,
   used up, washed-up, way-weary, wayworn, weak, weakened, wearied,
   weariful, weary, weary unto death, weary-footed, weary-laden,
   weary-winged, weary-worn, whacked, wilting, wiped out, worn,
   worn-down, worn-out