a calculation that results in an estimate that is too high an appraisal that is too high make too high an estimate of; "He overestimated his own powers
emphasis If you say that something cannot be overestimated, you are emphasizing that you think it is very important. The importance of participating in the life of the country cannot be overestimated It is hard to overestimate the potential gains from this process
If you say that someone overestimates something, you mean that they think it is greater in amount or importance than it really is. With hindsight, he was overestimating their desire for peace. underestimate Overestimate is also a noun. Average earnings in the South East were about £59,000, although that may be an overestimate. + overestimation over·es·ti·ma·tion excessive overestimation of one's own importance. underestimation
If you overestimate someone, you think that they have more of a skill or quality than they really have. I think you overestimate me, Fred. underestimate. a calculation, judgement, or guess that is too large