runaway
/ˈrʌnəˌweɪ/noun
1- a person who has run away, especially from their family or an institution（尤指从家庭或机构中）逃跑者, 出逃者。
1.1
- often as modifier an animal or vehicle that is running out of control脱缰的牲口; 失控的车辆：
a runaway train.
一列失控的火车。
1.2
- as modifier denoting something happening or done very quickly, easily, or uncontrollably迅速发生的; 轻易取得的; 控制不住的：
the runaway success of the book.
这本书的迅速走俏。