runaway
run-a-way
adjective
Having escaped or become out of control, often causing problems or rapid growth.
"The runaway train sped down the tracks."
noun
A person, especially a child or young person, who has run away from home.
"Police searched for the teenage runaway."
Thesaurus
Synonyms: uncontrolled, blowout, shoo-in, walkaway, romp, laugher, fugitive, fleer