Synonyms for Madcap (same or very similar meaning)
WordNet sense 1 (a reckless impetuous irresponsible person):
daredevil, harum-scarum, hothead, lunatic, swashbucklerWordNet sense 2 (characterized by undue haste and lack of thought or deliberation):
hotheaded, impetuous, impulsive, brainish, tearawayWordNet sense 3 (lacking in caution):
incautiousFrom the ODE community, based on WordNetadd/edit