From Longman Dictionary of Contemporary Englishmandolinman‧do‧lin, mandoline /ˌmændəˈlɪn/ noun [countable] 
APMa musical instrument with eight metal strings and a round back, played with a plectrum (=small piece of plastic, metal etc)
APMa musical instrument with eight metal strings and a round back, played with a plectrum (=small piece of plastic, metal etc)Examples from the Corpus
mandolin• Try comparing a plucked note on a violin and on a mandolin and you will certainly notice the difference.• A young fellow strummed on a mandolin and a woman sang a Hebrew song.• This can be done with the slicer blade of a food processor or a mandolin.• They had no mandolin but Ollie's guitar would do.• Brown learned to play guitar, violin, harmonica, piano, mandolin, viola and drums.• Yet the solo mandolin enjoyed a now-forgotten renaissance between about 1885 and 1920.• Gish died in 1993, but the mandolin is still with us.• And since the mandolin has a different tuning to the guitar, it gives you a different chord voicing to everybody else.Origin mandolin (1700-1800) Italian mandolina, from mandola “large type of mandolin”, from French mandore 