The Collaborative International Dictionary of English v.0.48:

Dab \Dab\ (d[a^]b), v. i. [imp. & p. p. Dabbed (d[a^]bd); p.
   pr. & vb. n. Dabbing.] [OE. dabben to strice; akin to OD.
   dabben to pinch, knead, fumble, dabble, and perh. to G.
   tappen to grope.]
   1. To strike or touch gently, as with a soft or moist
      substance; to tap; hence, to besmear with a dabber.
      [1913 Webster]

            A sore should . . . be wiped . . . only by dabbing
            it over with fine lint.               --S. Sharp.
      [1913 Webster]

   2. To strike by a thrust; to hit with a sudden blow or
      thrust. "To dab him in the neck." --Sir T. More.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dab \Dab\, n.
   1. A gentle blow with the hand or some soft substance; a
      sudden blow or hit; a peck.
      [1913 Webster]

            A scratch of her claw, a dab of her beak.
                                                  --Hawthorne.
      [1913 Webster]

   2. A small mass of anything soft or moist.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dab \Dab\ (d[a^]b), n. [Perh. corrupted fr. adept.]
   A skillful hand; a dabster; an expert. [Colloq.]
   [1913 Webster]

         One excels at a plan or the titlepage, another works
         away at the body of the book, and the third is a dab at
         an index.                                --Goldsmith.
   [1913 Webster] Dab

The Collaborative International Dictionary of English v.0.48:

Dab \Dab\, n. [Perh. so named from its quickness in diving
   beneath the sand. Cf. Dabchick.] (Zool.)
   A name given to several species of flounders, esp. to the
   European species, Pleuronectes limanda. The American rough
   dab is Hippoglossoides platessoides.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dab
    n 1: a light touch or stroke [syn: tap, pat, dab]
    2: a small quantity of something moist or liquid; "a dab of
       paint"; "a splatter of mud"; "just a splash of whiskey" [syn:
       dab, splash, splatter]
    v 1: apply (usually a liquid) to a surface; "dab the wall with
         paint" [syn: dab, swab, swob]
    2: hit lightly; "pat him on the shoulder" [syn: dab, pat]