Source : Webster's Revised Unabridged Dictionary (1913)

Plectrum \Plec"trum\, n.; pl. L. {Plectra}, E. Plectrums . [L.,
   fr. Gr. ? anything to strike with, fr.? to strike.]
   A small instrument of ivory, wood, metal, or quill, used in
   playing upon the lyre and other stringed instruments.

Source : WordNet®

plectron
     n : a small thin device (of metal or plastic or ivory) used to
         pluck a stringed instrument [syn: {pick}, {plectrum}]
     [also: {plectra} (pl)]

plectra
     See {plectron}