madcap I. \ˈ ̷ ̷ˌ ̷ ̷\noun Etymology:mad (I) + cap : one who is madcap II. adjective : marked by impulsiveness, recklessness, or rashness < the madcap girl ran up to her mother — W.M.Thackeray > < the venture was a sound proposition … no madcap haphazard scheme — Irish Digest >