Source : Webster's Revised Unabridged Dictionary (1913)

Nab \Nab\, v. t. [imp. & p. p. {Nabbed}; p. pr. & vb. n.
   {Nabbing}.] [Dan nappe, or Sw. nappa.]
   To catch or seize suddenly or unexpectedly. [Colloq.]
   --Smollett.

Nab \Nab\ (n[a^]b), n. [Cf. {Knap}, {Knop}, {Knob}.]
   1. The summit of an eminence. [Prov. Eng.] --Halliwell.

   2. (Firearms) The cock of a gunlock. --Knight.

   3. (Locksmithing) The keeper, or box into which the lock is
      shot. --Knight.

Source : WordNet®

nab
     v 1: tag the base runner to get him out
     2: take into custody; "the police nabbed the suspected
        criminals" [syn: {collar}, {nail}, {apprehend}, {arrest},
        {pick up}, {cop}]
     3: seize suddenly
     [also: {nabbing}, {nabbed}]