Merriam-Webster Collegiate Dictionary - slang

 I. noun  Etymology: origin unknown  Date: 1756  1. language peculiar to a particular group: as  a. argot  b. jargon 2  2. an informal nonstandard vocabulary composed typically of coinages, arbitrarily changed words, and extravagant, forced, or facetious figures of speech  • ~ adjective  • ~ily adverb  • ~iness noun  • ~y adjective  II. verb  Date: 1828  intransitive verb to use ~ or vulgar abuse  transitive verb to abuse with harsh or coarse language