Source : Webster's Revised Unabridged Dictionary (1913)

Clarinet \Clar"i*net`\, n. [F. clarinette, dim. of clarine, from
   L. clarus. See {Clear}, and cf. {Clarion}.] (Mus.)
   A wind instrument, blown by a single reed, of richer and
   fuller tone than the oboe, which has a double reed. It is the
   leading instrument in a military band.

   Note: [Often improperly called {clarionet}.]

Source : WordNet®

clarinet
     n : a single-reed instrument with a straight tube