[1] : WordNet (r) 2.0

headphone
     n : electro-acoustic transducer for converting electric signals
         into sounds; it is held over or inserted into the ear;
         "it was not the typing but the earphones that she
         disliked" syn: earphone, earpiece, phone
see also:
earphone earpiece phone 

[2] : Moby Thesaurus II by Grady Ward, 1.0

34 moby thesaurus words for "headphone":
   acoustical network, capacitor speaker, coaxial speaker, cone,
   crossover network, diaphragm, dynamic speaker, earphone,
   electrodynamic speaker, electromagnetic speaker,
   electrostatic speaker, excited-field speaker,
   full-fidelity speaker, headset, high-fidelity speaker,
   high-frequency speaker, horn, loudspeaker, low-frequency speaker,
   midrange speaker, monorange speaker, moving-coil speaker,
   permanent magnet speaker, radiophone, radiotelephone, speaker,
   speaker system, speaker unit, triaxial speaker, tweeter,
   voice coil, wireless, wireless telephone, woofer

Headphone >> H Words
Headphone, definition of term: Headphone
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