The Collaborative International Dictionary of English v.0.48:

ghetto blaster \ghetto blaster\ n. [from their popularity with
   negro inner-city (ghetto) youth]
   A portable casette or compact disk player, usually having an
   integrated radio receiver. It typically has two
   (stereophonic) speakers, and can be adjusted to play at a
   high sound intensity, from which the name comes.

   Syn: boom box.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

ghetto blaster
    n 1: a portable stereo [syn: ghetto blaster, boom box]