The Collaborative International Dictionary of English v.0.48:

Forlorn \For*lorn"\, a. [OE., p. p. of forlesen to lose utterly,
   AS. forle['o]san (p. p. forloren); pref. for- + le['o]san (in
   comp.) to lose; cf. D. verliezen to lose, G. verlieren, Sw.
   f["o]rlora, Dan. forloren, Goth. fraliusan to lose. See
   For-, and Lorn, a., Lose, v. t.]
   1. Deserted; abandoned; lost.
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            Of fortune and of hope at once forlorn. --Spenser.
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            Some say that ravens foster forlorn children.
                                                  --Shak.
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   2. Destitute; helpless; in pitiful plight; wretched;
      miserable; almost hopeless; desperate.
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            For here forlorn and lost I tread.    --Goldsmith.
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            The condition of the besieged in the mean time was
            forlorn in the extreme.               --Prescott.
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            She cherished the forlorn hope that he was still
            living.                               --Thomson.
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   A forlorn hope [D. verloren hoop, prop., a lost band or
      troop; verloren, p. p. of verliezen to lose + hoop band;
      akin to E. heap. See For-, and Heap.] (Mil.), a body
      of men (called in F. enfants perdus, in G. verlornen
      posten) selected, usually from volunteers, to attempt a
      breach, scale the wall of a fortress, or perform other
      extraordinarily perilous service; also, a desperate case
      or enterprise.

   Syn: Destitute, lost; abandoned; forsaken; solitary;
        helpless; friendless; hopeless; abject; wretched;
        miserable; pitiable.
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The Collaborative International Dictionary of English v.0.48:

Forlese \For*lese"\, v. t. [p. p. Forlore, Forlorn.] [OE.
   forlesen. See Forlorn.]
   To lose utterly. [Obs.] --haucer.
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The Collaborative International Dictionary of English v.0.48:

Forlorn \For*lorn"\, n.
   1. A lost, forsaken, or solitary person.
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            Forced to live in Scotland a forlorn. --Shak.
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   2. A forlorn hope; a vanguard. [Obs.]
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            Our forlorn of horse marched within a mile of the
            enemy.                                --Oliver
                                                  Cromvell.
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WordNet (r) 3.0 (2006):

forlorn
    adj 1: marked by or showing hopelessness; "the last forlorn
           attempt"; "a forlorn cause"

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "forlorn":
   abandoned, affording no hope, alone, apathetic, bereft, bleak,
   cheerless, comfortless, cynical, defenseless, dejected, depressed,
   deserted, desolate, desole, despairing, desperate, despondent,
   desponding, disconsolate, dismal, dispirited, dolorous, down,
   fatherless, forgotten, forsaken, friendless, fruitless, futile,
   gloomy, glum, godforsaken, grim, heartsick, heartsore, helpless,
   homeless, hopeless, in despair, inconsolable, joyless, kithless,
   lonely, lonesome, lost, low-spirited, lugubrious, melancholy,
   miserable, motherless, mournful, neglected, oppressed, outcast,
   pathetic, pessimistic, pitiable, pitiful, sad, shunned, sick,
   sick at heart, solitary, sorrowful, soul-sick, unconsolable,
   unfriended, unhappy, unhopeful, vain, without hope, woebegone,
   woeful, wretched