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.
      [1913 Webster]

            You tell him silver is scarcer now in England, and
            therefore risen one fifth in value.   --Locke.
      [1913 Webster]

            The scarcest of all is a Pescennius Niger on a
            medallion well preserved.             --Addison.
      [1913 Webster]

   2. Scantily supplied (with); deficient (in); -- with of.
      [Obs.] "A region scarce of prey." --Milton.
      [1913 Webster]

   3. Sparing; frugal; parsimonious; stingy. [Obs.] "Too scarce
      ne too sparing." --Chaucer.
      [1913 Webster]

   To make one's self scarce, to decamp; to depart. [Slang]
      [1913 Webster]

   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.
      [1913 Webster]

            With a scarce well-lighted flame.     --Milton.
      [1913 Webster]

            The eldest scarcely five year was of age. --Chaucer.
      [1913 Webster]

            Slowly she sails, and scarcely stems the tides.
                                                  --Dryden.
      [1913 Webster]

            He had scarcely finished, when the laborer arrived
            who had been sent for my ransom.      --W. Irving.
      [1913 Webster]

   2. Frugally; penuriously. [Obs.] --Chaucer.
      [1913 Webster]

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]