cowboy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A hired man, especially in the western United States, who tends cattle and performs many of his duties on horseback.
• noun An adventurous hero.
• noun Slang A reckless person, such as a driver, pilot, or manager, who ignores potential risks.

from The Century Dictionary.

• noun A boy who takes charge of cows or drives them to and from pasture.
• noun On the great plains of the western United States, a man employed by a stockman or ranchman in the care of grazing cattle, doing his work on horseback.
• noun One of a band of marauders during the American revolution, chiefly refugees belonging to the British side, who infested the neutral ground between the British and American lines in the neighborhood of New York, and plundered the whigs or revolutionists.

from the GNU version of the Collaborative International Dictionary of English.

• noun A cattle herder; a drover; specifically, one of an adventurous class of herders and drovers on the plains of the Western and Southwestern United States.
• noun One of the marauders who, in the Revolutionary War infested the neutral ground between the American and British lines, and committed depredations on the Americans.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A man who tends free-range cattle, especially in the American West.
• noun A man who identifies with cowboy culture, including wearing a cowboy hat and being a fan of country and western music.
• noun informal A person who engages in reckless behavior, especially for the purpose of showing off.
• noun UK, informal A dishonest and/or incompetent independent tradesman.
• noun A playing card of king rank.
• verb intransitive To work as a cowboy, herding cattle.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun someone who is reckless or irresponsible (especially in driving vehicles)
• noun a hired hand who tends cattle and performs other duties on horseback
• noun a performer who gives exhibitions of riding and roping and bulldogging