An underachiever is a person and especially a student who fails to achieve his or her potential or does not do as well as expected.
Of particular interest is academic underachievement. Studies of individuals who have not realised their apparent potential have identified learning disabilities, ADD, and many other educational problems, and enabled methods of addressing these problems to be developed. Current theories among academic scholars prefer to address underperformance problems with remedial help. Academic under-achievement can also be attributed to relatively intelligent or gifted students, but they do not perform as expected either because they are bored or choose not to excel.
The term is also used more generally, for example a team that contains many star players but still loses games against teams with relatively little obvious talent would be termed underachieving. A stock which achieves poor profit and/or capital gains despite sound underlying business and/or asset backing may be called underachieving.