[n] a reckless impetuous irresponsible person
[adj] 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)
1. Inclined to wild sports; delighting in rash, absurd, or dangerous amusements. ``The merry madcap lord.'' --Shak.
2. Wild; reckless. ``Madcap follies'' --Beau. & Fl.
\Mad"cap`\, n. A person of wild behavior; an excitable, rash, violent person. --Shak.