In the field of psychology, the term “overachiever” refers to an individual who pushes him- or herself to achieve success in his or her chosen field of study or work, sometimes to an extreme, and sometimes beyond others’ expectations of what that individual is capable of achieving. Overachievers are generally considered to be exceptionally organized, hard-working, and prone to isolating themselves from the social activities of their peers in order to remain focused on the task at hand. One professional psychologist, quoted below, uses the standard dictionary definition of “overachiever” for the purposes of discussion:
“As a psychologist specializing in anxiety and depression, I have met a good number of overachievers in my practice. Merriam-Webster defines an overachiever as ‘one who achieves success over and above the standard or expected level especially at an early age’.” [http://rosspsychology.com/1/post/2010/07/plague-of-the-overachiever.html]
While this particular psychologist views overachievers as suffering from a personality disorder, referring to it as “a plague of habits that often must be acknowledged,” including performance in school and work, and including “darker roots and beliefs about why ‘we must achieve’,” others take a decidedly more optimistic view of overachievers. John Eliot, another psychologist specializing in the study of overachievers, contends that common perceptions about such individuals tend to exaggerate the degree to which there is any kind of personality disorder. Rather, according to Eliot, overachievers are notable for their determination to achieve a high level of performance while most of the rest of society aims for mediocrity. Eliot does not dismiss the exceptionalism of overachievers; as he notes, "Overachievers don't think reasonably, sensibly or rationally." The rational, he suggests, are those who strive for mediocrity. As noted in an article on his theory of overachievers:
“To ratchet up your performance to the exceptional range, you really have to BE an exception. You have to thrive under pressure—welcome pressure, enjoy it and make it work to your advantage.” [http://www.psychologytoday.com/articles/200412/the-overachievers]
To conclude, then, overachievers are individuals who strive for excellence, and are willing to make the extra effort necessary to accomplish that goal. In everyday conversation, however, the term will continue to be applied to individuals who exceed expectations.
Someone who pushes themselves to the extreme to get things done. Goes over the top to do great in a subject. FOr example, if you have a project coming up and you do the average amount needed that's different than spending hours, decorating it, making it perfect just to OVER achieve the goal that is set