underachiever

Definition of Underachiever in English :

a student who does not perform as well as expected or as well as the IQ indicates

WordNet Lexical Database for English. Princeton University. 2010.

Underachiever

verb

(intransitive)

to fail to achieve a performance appropriate to one's age or talents

verb intransitiveWord forms: ˌunderaˈchieved or ˌunderaˈchieving

1.

to fail to do as well in school studies as might be expected from scores made on intelligence tests

2.

to perform below expectations

intr.v. un·der·a·chieved, un·der·a·chiev·ing, un·der·a·chieves

To perform worse or achieve less success than expected.