The Collaborative International Dictionary of English v.0.48:

Scarce \Scarce\ (sk[^a]rs), a. [Compar. Scarcer
   (sk[^a]r"s[~e]r); superl. Scarcest.] [OE. scars, OF.
   escars, eschars, LL. scarpsus, excarpsus, for L. excerptus,
   p. p. of excerpere to pick out, and hence to contract, to
   shorten; ex (see Ex-) + carpere. See Carpet, and cf.
   Excerp.]
   1. Not plentiful or abundant; in small quantity in proportion
      to the demand; not easily to be procured; rare; uncommon.
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            You tell him silver is scarcer now in England, and
            therefore risen one fifth in value.   --Locke.
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            The scarcest of all is a Pescennius Niger on a
            medallion well preserved.             --Addison.
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   2. Scantily supplied (with); deficient (in); -- with of.
      [Obs.] "A region scarce of prey." --Milton.
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   3. Sparing; frugal; parsimonious; stingy. [Obs.] "Too scarce
      ne too sparing." --Chaucer.
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   To make one's self scarce, to decamp; to depart. [Slang]
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   Syn: Rare; infrequent; deficient. See Rare.
        [1913 Webster] Scarce

The Collaborative International Dictionary of English v.0.48:

Scarce \Scarce\, Scarcely \Scarce"ly\, adv.
   1. With difficulty; hardly; scantly; barely; but just.
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            With a scarce well-lighted flame.     --Milton.
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            The eldest scarcely five year was of age. --Chaucer.
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            Slowly she sails, and scarcely stems the tides.
                                                  --Dryden.
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            He had scarcely finished, when the laborer arrived
            who had been sent for my ransom.      --W. Irving.
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   2. Frugally; penuriously. [Obs.] --Chaucer.
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WordNet (r) 3.0 (2006):

scarce
    adv 1: only a very short time before; "they could barely hear
           the speaker"; "we hardly knew them"; "just missed being
           hit"; "had scarcely rung the bell when the door flew
           open"; "would have scarce arrived before she would have
           found some excuse to leave"- W.B.Yeats [syn: barely,
           hardly, just, scarcely, scarce]
    adj 1: deficient in quantity or number compared with the demand;
           "fresh vegetables were scarce during the drought" [ant:
           abundant]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "scarce":
   almost unheard-of, at a premium, barely, cheeseparing, chinchy,
   chintzy, curtailed, deficient, exiguous, failing, few, hardly,
   in short supply, inadequate, infrequent, insufficient, lacking,
   meager, miserly, niggardly, occasional, out of print,
   out of season, out of stock, piddling, poor, rare, scant, scanty,
   scarcely, scattered, scrimping, scrimpy, seldom, seldom met with,
   seldom seen, shortened, shy, skimping, skimpy, slim, slow, sparse,
   sporadic, spotty, sprinkled, stingy, thin, tight, truncated,
   uncommon, unfrequent, unique, unusual, wanting