Source : Webster's Revised Unabridged Dictionary (1913)

Prodrome \Pro"drome\, n. [Gr. ? running before; ? before + ? to
   run: cf. F. prodrome.]
   A forerunner; a precursor.

Source : WordNet®

prodrome
     n : an early symptom that a disease is developing or that an
         attack is about to occur [syn: {prodroma}]