from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Behaving or acting impulsively or rashly; wild.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. impulsive, hasty or reckless; capricious.
- n. An impulsive, hasty, capricious person.
- n. An insane person, a lunatic.
from the GNU version of the Collaborative International Dictionary of English
- adj. Inclined to wild sports; delighting in rash, absurd, or dangerous amusements.
- adj. Wild; reckless.
- n. A person of wild behavior; an excitable, rash, violent person.
from The Century Dictionary and Cyclopedia
- n. A person who acts madly or wildly; a flighty or harebrained person; one who indulges in frolics.
- Pertaining to or resembling a madcap; wild; harum-scarum.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. characterized by undue haste and lack of thought or deliberation
- n. a reckless impetuous irresponsible person
mad + cap1, head.(American Heritage® Dictionary of the English Language, Fourth Edition)
1580s, mad + cap (“head”), literally “crazy head”. Original literal sense “lunatic, crazy person”, now used figuratively. (Wiktionary)