Source : Webster's Revised Unabridged Dictionary (1913)

Misestimate \Mis*es"ti*mate\, v. t.
   To estimate erroneously. --J. S. Mill.

Source : WordNet®

misestimate
     v 1: judge incorrectly; "I had misestimated his determination"
          [syn: {miscalculate}]
     2: calculate incorrectly; "I miscalculated the number of guests
        at the wedding" [syn: {miscalculate}]