Urban Dictionary - Urban Dictionary is a Web-based dictionary of slang words and phrases.
The Online Slang Dictionary - Learn thousands of real slang words or add your own.
SlangLang - SlangLang is an editorial dictionary for slang words mainly used on the internet. Here you will find definitions and information about the origin and spread of terms, memes and emotes that are used on the net.
Wedefine - Wedefine is an open source dictionary site that you can self host
SlangSite.com - SlangSite.
Slang-Dictionary.org - Slang-Dictionary is a web-based database for searching through the database of slang words and learn how different words are getting different meanings in different countries of the world.