Source : Webster's Revised Unabridged Dictionary (1913)

Banderilla \Ban`de*ril"la\, n. [Sp., dim. of bandera banner. See
   {Banner}, and cf. {Banderole}.]
   A barbed dart carrying a banderole which the banderillero
   thrusts into the neck or shoulder of the bull in a bullfight.

Source : WordNet®

banderilla
     n : a decorated dart that is implanted in the neck or shoulders
         of the bull during a bull fight