Source : Webster's Revised Unabridged Dictionary (1913)

Mandolin \Man"do*lin\, Mandoline \Man"do*line\, n. [F.
   mandoline, It. mandolino, dim. of mandola, fr. L. pandura.
   See {Bandore}.] (Mus.)
   A small and beautifully shaped instrument resembling the
   lute.

Source : WordNet®

mandolin
     n : a stringed instrument related to the lute, usually played
         with a plectrum