harum-scarum

(noun) a reckless impetuous irresponsible person. Synonyms: daredevil, madcap, hothead, swashbuckler, lunatic.

(adj) cheerfully irresponsible. Synonyms: carefree, devil-may-care, freewheeling, happy-go-lucky, slaphappy. Examples: "Carefree with his money." "Freewheeling urban youths." "Had a harum-scarum youth."

(adv) in a wild or reckless manner. Synonyms: pell-mell. Examples: "Dashing harum-scarum all over the place." "Running pell-mell up the stairs."