What is the meaning of overestimate?

noun

• An appraisal that is too high.
  • synonyms: overestimation, overvaluation, overappraisal
• A calculation that results in an estimate that is too high.
  • synonyms: overestimation, overrating, overreckoning

verb

• Make too high an estimate of.
  • usage: "He overestimated his own powers"
  • synonyms: overrate
• Assign too high a value to.
  • usage: "You are overestimating the value of your old car"
  • synonyms: overvalue