From The Art and Popular Culture Encyclopedia
Slang is the use of informal words and expressions to describe an object or condition. Slang is vocabulary that is meant to be interpreted quickly but not necessarily literally, as slang words or terms are often a metaphor or an allegory.
Slang is sometimes regional in that it is only used in a particular territory. Slang terms are frequently particular to a certain subculture, such as musicians, and members of minority groups. Nevertheless, usage of slang expressions can spread outside their original arenas to become commonly used, such as "cool" and "jive". While some words eventually lose their status as slang, others continue to be considered as such by most speakers. In spite of this, the process tends to lead the original users to replace the words with other, less-recognized terms to maintain group identity.