wild child          
noun [ C ] uk/ˈwaɪld ˌtʃaɪld/ us/ˈwaɪld ˌtʃaɪld/
 (行为不受控制、叛逆、酗酒等的)野孩子
a young person who acts in an uncontrolled way, for example not obeying their parents, drinking too much alcohol, etc.
  She was a wild child when younger, but is now clean and sober.  她年轻的时候是个野孩子,但现在已经戒掉,不再酗酒了。 
  野孩子
a child who has grown up separated from normal human society
  He researched tales of wild children - either those who had grown up alone or with animals. 他研究了野孩子的故事——在野外独自长大或和动物一起长大的孩子。 
 - More examples
 - When the author was 15, she was a wild child who acted up by drinking, dating a drug dealer, and running away from home.
 - Who was she exactly? An out-of-control wild child, or a home-loving girl who fell into bad company?
 - Friends said he was a wild child, but he was never looked on as a troublemaker.
 - Many of the stories of wild children found living with wolves end tragically because they cannot adapt to their new environment.
 - If language and communication define an important aspect of humanity can Peter and the other wild children ever be assimilated back into society without it?