runaway
UK: ˈrʌnəweɪ | US: ˈrʌnəweɪ
n. a person who has fled or escaped, especially from home or control
adj. (of an event or process) proceeding uncontrollably or without restraint
The word "runaway" combines "run" (Old English rinnan, meaning "to move swiftly on foot") and "away" (Old English onweg, meaning "from a place"). Originally used literally for someone fleeing, it later expanded metaphorically to describe uncontrollable situations (e.g., "runaway inflation"). The morphemes preserve their original meanings while forming a cohesive compound.
The runaway child was found safe by the police.
The film tells the story of a teenage runaway seeking freedom.
The company faced a runaway success with its new product.
She struggled to control the runaway horse.
Runaway costs forced the project to shut down.