adult noun
ADJ. young This book will definitely appeal to teenagers and young adults. | single The number of single adult households has doubled in the past 30 years. | consenting What consenting adults do in private is their own business. | responsible I simply can't believe that responsible adults allowed a child to wander the streets.
ADULT + NOUN life She spent her entire adult life caring for others. | education, literacy | population
You can also check other dicts: adult (English, 中文解释 ), wordnet sense, Collins Definition