WordNet (r) 3.0 (2006):

public address system
    n 1: an electronic amplification system used as a communication
         system in public areas [syn: public address system, P.A.
         system, PA system, P.A., PA]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "public address system":
   Gramophone, PA, PA system, Victrola, audio sound system,
   audiophile, binaural system, bitch box, bullhorn, cartridge,
   ceramic pickup, changer, crystal pickup,
   derived four-channel system, discrete four-channel system,
   four-channel stereo system, hi-fi, hi-fi fan, high-fidelity,
   intercom, intercommunication system, jukebox, magnetic pickup,
   monaural system, mono, needle, nickelodeon, phonograph,
   photoelectric pickup, pickup, quadraphonic sound system,
   radio-phonograph combination, record changer, record player,
   sound reproduction system, sound truck, squawk box, stereo, stylus,
   system, tape deck, tape recorder, tone arm,
   transcription turntable, turntable