[1] : The Collaborative International Dictionary of English v.0.48

earpiece \earpiece\ n.
   a device for converting electric signals into sounds,
   designed to be held over or inserted into the ear; as, the
   common telephone handset has a speaker and an earpiece.

   syn: earphone, headphone, phone.
        wordnet 1.5

[2] : WordNet (r) 2.0

earpiece
     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, headphone, phone
see also:
earphone headphone phone 

Earpiece >> E Words
Earpiece, definition of term: Earpiece
earpiece_pag1.html