Source : Webster's Revised Unabridged Dictionary (1913)

Leitmotif \Leit"mo*tif"\ (l[imac]t"m[-o]*t[-e]f"), n. [G.]
   (Mus.)
   See {Leading motive}, under {Leading}, a.

Source : WordNet®

leitmotif
     n : a melodic phrase that accompanies the reappearance of a
         person or situation (as in Wagner's operas) [syn: {leitmotiv}]