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1. An appraisal that is too high
   - overestimation, overvaluation, overappraisal
    
2. A calculation that results in an estimate that is too high
   - overestimation, overrating, overreckoning

1. Make too high an estimate of
   "He overestimated his own powers";
   - overrate
    
2. Assign too high a value to
   "You are overestimating the value of your old car";
   - overvalue

Derived forms: overestimated, overestimates, overestimating

See also: approximate

Type of: appraisal, approximation, estimate, estimation, idea, misjudge, value

Antonym: underrate, undervalue

Encyclopedia: Overestimate