Source : Webster's Revised Unabridged Dictionary (1913)

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