Source : Webster's Revised Unabridged Dictionary (1913)

Melodrama \Mel`o*dra"ma\, n. [F. m['e]lodrame, fr. Gr. ? song +
   ? drama.]
   Formerly, a kind of drama having a musical accompaniment to
   intensify the effect of certain scenes. Now, a drama
   abounding in romantic sentiment and agonizing situations,
   with a musical accompaniment only in parts which are
   especially thrilling or pathetic. In opera, a passage in
   which the orchestra plays a somewhat descriptive
   accompaniment, while the actor speaks; as, the melodrama in
   the gravedigging scene of Beethoven's ``Fidelio''.

Source : WordNet®

melodrama
     n : an extravagant comedy in which action is more salient than
         characterization