The Collaborative International Dictionary of English v.0.48:

Sharp \Sharp\, a. [Compar. Sharper; superl. Sharpest.] [OE.
   sharp, scharp, scarp, AS. scearp; akin to OS. skarp, LG.
   scharp, D. scherp, G. scharf, Dan. & Sw. skarp, Icel. skarpr.
   Cf. Escarp, Scrape, Scorpion.]
   1. Having a very thin edge or fine point; of a nature to cut
      or pierce easily; not blunt or dull; keen.
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            He dies upon my scimeter's sharp point. --Shak.
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   2. Terminating in a point or edge; not obtuse or rounded;
      somewhat pointed or edged; peaked or ridged; as, a sharp
      hill; sharp features.
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   3. Affecting the sense as if pointed or cutting, keen,
      penetrating, acute: to the taste or smell, pungent, acid,
      sour, as ammonia has a sharp taste and odor; to the
      hearing, piercing, shrill, as a sharp sound or voice; to
      the eye, instantaneously brilliant, dazzling, as a sharp
      flash.
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   4. (Mus.)
      (a) High in pitch; acute; as, a sharp note or tone.
      (b) Raised a semitone in pitch; as, C sharp (C[sharp]),
          which is a half step, or semitone, higher than C.
      (c) So high as to be out of tune, or above true pitch; as,
          the tone is sharp; that instrument is sharp. Opposed
          in all these senses to flat.
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   5. Very trying to the feelings; piercing; keen; severe;
      painful; distressing; as, sharp pain, weather; a sharp and
      frosty air.
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            Sharp misery had worn him to the bones. --Shak.
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            The morning sharp and clear.          --Cowper.
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            In sharpest perils faithful proved.   --Keble.
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   6. Cutting in language or import; biting; sarcastic; cruel;
      harsh; rigorous; severe; as, a sharp rebuke. "That sharp
      look." --Tennyson.
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            To that place the sharp Athenian law
            Can not pursue us.                    --Shak.
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            Be thy words severe,
            Sharp as merits but the sword forbear. --Dryden.
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   7. Of keen perception; quick to discern or distinguish;
      having nice discrimination; acute; penetrating; sagacious;
      clever; as, a sharp eye; sharp sight, hearing, or
      judgment.
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            Nothing makes men sharper . . . than want.
                                                  --Addison.
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            Many other things belong to the material world,
            wherein the sharpest philosophers have never ye?
            arrived at clear and distinct ideas.  --L. Watts.
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   8. Eager in pursuit; keen in quest; impatient for
      gratification; keen; as, a sharp appetite.
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   9. Fierce; ardent; fiery; violent; impetuous. "In sharp
      contest of battle." --Milton.
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            A sharp assault already is begun.     --Dryden.
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   10. Keenly or unduly attentive to one's own interest; close
       and exact in dealing; shrewd; as, a sharp dealer; a sharp
       customer.
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             The necessity of being so sharp and exacting.
                                                  --Swift.
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   11. Composed of hard, angular grains; gritty; as, sharp sand.
       --Moxon.
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   12. Steep; precipitous; abrupt; as, a sharp ascent or
       descent; a sharp turn or curve.
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   13. (Phonetics) Uttered in a whisper, or with the breath
       alone, without voice, as certain consonants, such as p,
       k, t, f; surd; nonvocal; aspirated.
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   Note: Sharp is often used in the formation of self-explaining
         compounds; as, sharp-cornered, sharp-edged,
         sharp-pointed, sharp-tasted, sharp-visaged, etc.
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   Sharp practice, the getting of an advantage, or the attempt
      to do so, by a tricky expedient.

   To brace sharp, or To sharp up (Naut.), to turn the yards
      to the most oblique position possible, that the ship may
      lie well up to the wind.
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   Syn: Keen; acute; piercing; penetrating; quick; sagacious;
        discerning; shrewd; witty; ingenious; sour; acid; tart;
        pungent; acrid; severe; poignant; biting; acrimonious;
        sarcastic; cutting; bitter; painful; afflictive;
        violent; harsh; fierce; ardent; fiery.
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The Collaborative International Dictionary of English v.0.48:

Sharper \Sharp"er\, n.
   A person who bargains closely, especially, one who cheats in
   bargains; a swinder; also, a cheating gamester.
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         Sharpers, as pikes, prey upon their own kind.
                                                  --L'Estrange.
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   Syn: Swindler; cheat; deceiver; trickster; rogue. See
        Swindler.
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WordNet (r) 3.0 (2006):

sharper
    n 1: a professional card player who makes a living by cheating
         at card games [syn: cardsharp, card sharp,
         cardsharper, card sharper, sharper, sharpie,
         sharpy, card shark]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "sharper":
   adventurer, betting ring, bettor, boneshaker, bunco artist,
   bunco steerer, cardshark, cardsharp, cardsharper, carpetbagger,
   cheat, compulsive gambler, con artist, con man, confidence man,
   crap shooter, crimp, defrauder, diddler, double-dealer, gambler,
   gamester, gyp, hazarder, horse coper, horse trader, jackleg,
   land pirate, land shark, land-grabber, mortgage shark, mountebank,
   pettifogger, petty gambler, piker, pitchman, player, plunger,
   punter, shark, sharp, sharpie, shortchanger, shyster, slicker,
   speculator, spieler, sport, sporting man, sportsman, tinhorn,
   tipster, tout, trickster, venturer, wagerer