Dude is English slang for an individual, typically male. From the 1870s to the 1960s, dude primarily meant a person who dressed in an extremely fashionable manner or a conspicuous citified person who was visiting a rural location, a "city slicker". In the 1960s, dude evolved to mean any male person, a meaning that slipped into mainstream American slang in the 1970s. Current slang retains at least some use of all three of these common meanings.
