A Dictionary of Slang: English slang and colloquialisms currently used in the UK.
Businessballs.com - Cockney Rhyming Slang: Origins, derivations and dictionary translations. Cockney rhyming slang uses substitute words, usually two, as a coded alternative for another word.
Carleton County Colloquialisms: Dictionary of the colloquial language of Carleton County, New Brunswick, Canada and Aroostook County, Maine, USA. Audio clips accompany each entry.
Chinese-English Slang Translations: Various expressions, usually colloquialisms or slang, translated for the benefit of native Chinese speakers learning English.
Double-Tongued Word Wrester: A growing dictionary of words from the fringes of English, including jargon, slang, and loan words.
Insultmonger.com: An alphabetized compendium of expressions considered offensive, vituperative, and insulting.
London Slang: Online word and phrase dictionary of Cockney rhyming slang. Also includes examples of film slang.
PseudoDictionary: Covers slang, made up words, "webspeak", colloquialisms and accepts contributions for new entries.
Sayings Explained: Searchable database of well-known sayings, phrases, and slang, along with definitions and origins.
Slang Search: Definitions of common words in English-language slang, organized by subject area.
SlangSite.com: A dictionary of slang, webspeak, made up words, and colloquialisms. Submissions welcome.
The New American Sub-Standard Politically Incorrect Dictionary: A glossary of offensive terms or terms with offensive meanings.
The Online Slang Dictionary: A global dictionary of English slang.
Urban Dictionary: U.S. slang dictionary whose submissions and various definitions are subject to votes for inclusion.
