underachieve
— Verb
– English
~ perform less well or with less success than expected; "John consistently underachieves, although he is very able"; "My stocks underperformed last year"
underachievement
— Noun
– English
~ poorer than expected performance (poorer than might have been predicted from intelligence tests)
underachiever
— Noun
– English
~ a student who does not perform as well as expected or as well as the IQ indicates
underact
— Verb
– English
~ act (a role) with great restraint
underactive
— Adjective
– English
~ abnormally inactive
underage
— Adjective
– English
~ not of legal age; "minor children"
underage
— Adjective
– English
~ dependent by virtue of youth
underarm
— Adverb
– English
~ with the hand swung below shoulder level; "throwing a ball underarm"
underarm
— Adjective
– English
~ with hand brought forward and up from below shoulder level; "an underhand pitch"; "an underhand stroke"
underbelly
— Noun
– English
~ the soft belly or underside of an animal's body
underbelly
— Noun
– English
~ the quality of being weak or unprotected; "the soft underbelly of the Axis"- Winston Churchill