Source : Webster's Revised Unabridged Dictionary (1913)

Mispronounce \Mis`pro*nounce"\, v. t. & i. [imp. & p. p.
   {Mispronounced}; p. pr. & vb. n. {Mispronouncing}.]
   To pronounce incorrectly.

Source : WordNet®

mispronounce
     v : pronounce a word incorrectly