The Collaborative International Dictionary of English v.0.48:

Flageolet \Flag"eo*let`\, n. [F. flageolet, dim. of OF. flaj?l
   (as if fr. a LL. flautio;us), of fla["u]te, flahute, F.
   fl?te. See Flute.] (Mus.)
   A small wooden pipe, having six or more holes, and a
   mouthpiece inserted at one end. It produces a shrill sound,
   softer than of the piccolo flute, and is said to have
   superseded the old recorder.
   [1913 Webster]

   Flageolet tones (Mus.), the naturel harmonics or overtones
      of stringed instruments.
      [1913 Webster]