Source : Webster's Revised Unabridged Dictionary (1913)

Promissory \Prom"is*so*ry\, a.
   Containing a promise or binding declaration of something to
   be done or forborne.

   {Promissory note} (Law), a written promise to pay to some
      person named, and at a time specified therein, or on
      demand, or at sight, a certain sum of money, absolutely
      and at all events; -- frequently called a {note of hand}.
      --Kent. Byles. Story.

Source : WordNet®

promissory
     adj : relating to or having the character of a promise;
           "promissory note"