latchkey kid
noun [ C ] old-fashioned informal uk/ˈlætʃ.kiː ˌkɪd/ us/ˈlætʃ.kiː ˌkɪd/ (also latchkey child)
（因父母均工作放学后独自在家的）挂钥匙儿童
a child who has a key to his or her home and is often alone at home after school has finished for the day because his or her parents are out at work