Source : Webster's Revised Unabridged Dictionary (1913)

Spinet \Spin"et\, n. [OF. espinete, F. ['e]pinette (cf. It.
   spinetta), fr. L. spina a thorn; -- so called because its
   quills resemble thorns. See {Spine}.] (Mus.)
   A keyed instrument of music resembling a harpsichord, but
   smaller, with one string of brass or steel wire to each note,
   sounded by means of leather or quill plectrums or jacks. It
   was formerly much used.

   {Dumb spinet}. (Mus.) See {Manichordon}.

Spinet \Spi"net\, n. [L. spinetum. See {Spinny}.]
   A spinny. [Obs.] --B. Jonson.

Source : WordNet®

spinet
     n 1: small and compactly built upright piano
     2: early model harpsichord with only one string per note