"Dude"

The term "dude" is best known as a widely-used English slang word commonly used to informally address or refer to a person of the male sex. The word may also be used in the same manner when speaking to (or about) a person of the female sex. In typical formality social situations, it is not uncommon for young men to use the word "dude" to address one another. "Dude" may also be used alone in a sentence, serving as an exclamation; denoting a feeling of surprise, happiness, disappointment, amazement or anger, among other emotions.[1] The word might also be used practically anywhere in a sentence in order to convey such sentiments in conversation. The word's pluralization, simply "dudes," may also be used in the same manners.
Other definitions of dude exist; as a noun to describe a particularly well-dressed male or alternatively to describe one who is unfamiliar with life outside a large city. These definitions may be seen by some to go hand-and-hand: it is likely that someone raised in a large city (ex. New York City) may appear better dressed than, for example, a cattle rancher in the more open lands of California; hence the phrased definition "An Easterner in the West" (United States).[2]

http://en.wikipedia.org/wiki/Dude