Source : Webster's Revised Unabridged Dictionary (1913)

Overrate \O`ver*rate"\, v. t. [imp. & p. p. {Overrated}; p. pr.
   & vb. n. {Overrating}.]
   To rate or value too highly.

Overrate \O"ver*rate`\, n.
   An excessive rate. [R.] --Massinger.

Source : WordNet®

overrate
     v : make too high an estimate of; "He overestimated his own
         powers" [syn: {overestimate}] [ant: {underestimate}]