NOUN (2)

1. a stringed instrument used in American folk music; an elliptical body and a fretted fingerboard and three strings;

2. a trapezoidal zither whose metal strings are struck with light hammers;

The Collaborative International Dictionary of English v.0.48:

Dulcimer \Dul"ci*mer\, n. [It. dolcemele,r Sp. dulcemele, fr. L.
   dulcis sweet + melos song, melody, Gr. ?; cf. OF. doulcemele.
   See Dulcet, and Melody.] (Mus.)
   (a) An instrument, having stretched metallic wires which are
       beaten with two light hammers held in the hands of the
       performer.
   (b) An ancient musical instrument in use among the Jews.
       --Dan. iii. 5. It is supposed to be the same with the
       psaltery.
       [1913 Webster]

WordNet (r) 3.0 (2006):

dulcimer
    n 1: a stringed instrument used in American folk music; an
         elliptical body and a fretted fingerboard and three strings
    2: a trapezoidal zither whose metal strings are struck with
       light hammers