characterized by undue haste and lack of thought or deliberation; "a hotheaded decision"; "liable to such impulsive acts as hugging strangers"; "an impetuous display of spending and gambling"; "madcap escapades"; (`brainish' is archaic)
If you refer to a young person as a tearaway, you mean that they behave in a wild and uncontrolled way. He blamed lack of parental control for the young tearaways' behaviour. a young person who behaves badly and often gets into trouble