The Collaborative International Dictionary of English v.0.48:

Grab \Grab\, n.
   1. A sudden grasp or seizure.
      [1913 Webster]

   2. An instrument for clutching objects for the purpose of
      raising them; -- specially applied to devices for
      withdrawing drills, etc., from artesian and other wells
      that are drilled, bored, or driven.
      [1913 Webster]

   Grab bag, at fairs, a bag or box holding small articles
      which are to be drawn, without being seen, on payment of a
      small sum. [Colloq.]

   Grab game, a theft committed by grabbing or snatching a
      purse or other piece of property. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

grab bag
    n 1: an assortment of miscellaneous items
    2: a container from which a person draws a wrapped item at
       random without knowing the contents