un·der·achiev·er 
/ˌʌndɚrəˈtʃi:vɚ/ noun
plural un·der·achiev·ers /ˌʌndɚrəˈtʃi:vɚ/ noun [count] : someone (such as a student or athlete) who does not perform as well or work as hard as he or she can — opposite overachiever
— un·der·achieve /ˌʌndɚrəˈtʃi:v/ verb, un·der·achieves; un·der·achieved; un·der·achiev·ing [no obj]
▪ Many students underachieve during their senior year.
/ˌʌndɚrəˈtʃi:v/ verb, un·der·achieves; un·der·achieved; un·der·achiev·ing [no obj] ▪ Many students underachieve during their senior year.
— un·der·achieve·ment /ˌʌndɚrəˈtʃi:v/ noun [noncount]
/ˌʌndɚrəˈtʃi:v/ noun [noncount]
