Looking for a definition? Internet addresses are provided below for general English language and subject specific dictionaries:

General English Language Dictionaries:

• Cambridge Dictionaries Online
  dictionary.cambridge.org/
• Chambers Reference Online (incl. dictionary, biographical dictionary and thesaurus)
  www.chambersharrap.co.uk/chambers/features/chref/chref.py/main
• Dictionary of Phrase & Fable (Brewer's)
  www.bartleby.com/81/
• The Glossarist (directory of glossaries on the Internet)
  www.glossarist.com/
• The HyperDictionary
  www.hyperdictionary.com/
• Merriam-Webster Online
  www.merriam-webster.com/
• One Look Dictionaries
  www.onelook.com/
• One Look Reverse Dictionary
  www.onelook.com/reverse-dictionary.shtml
• Thesaurus.com
  thesaurus.reference.com/

Specialty Dictionaries:

Art:

• ArtLex: Dictionary of Visual Art
  www.artlex.com/

Chemistry:

• IUPAC Compendium of Chemical Terminology (International Union of Pure and Applied Chemistry)
  goldbook.iupac.org/

Computing:

• Babel: A Glossary of Computer Oriented Abbreviations & Acronyms
  www.cs.tut.fi/tlt/stuff/misc/babel.html
• Computer User High-Tech Dictionary
  www.computeruser.com/resources/dictionary/
• Free Online Dictionary of Computing
  foldoc.org/
• Whatis.com
  whatis.techtarget.com/

Cooking:

• Epicurious Food Dictionary
  www.epicurious.com/tools/fooddictionary/
• Spice and Herb Encyclopedia
  www.culinarycafe.com/Spices_Herbs/index.html
  

Etymology:

• Online Etymology Dictionary
  www.etymonline.com/

Languages:

• ARTFL: French-English Dictionary
  humanities.uchicago.edu/orgs/ARTFL/forms_unrest/FR-ENG.html
• WordReference.com: Online French, Italian, and Spanish Dictionary

www.wordreference.com/

Law:

• Duhaime's Legal Dictionary
  www.duhaime.org/dictionary/diction.aspx
• The 'Lectric Law Library's Legal Lexicon
  www.lectlaw.com/def.htm

Medicine:

• Medilexicon (incl. medical, pharmaceutical, biomedical, and health care acronyms and abbreviations)
  www.medilexicon.com/
• MEDLINEplus Medical Encyclopedia
  www.nlm.nih.gov/medlineplus/mplusdictionary.html
• Medterms
  www.medterms.com/
• Who Named it? (incl. medical phenomena named for a person, eg. Graves' disease)
  www.whonamedit.com/

Mining:

• InfoMine Dictionary of Mining Terms
  xmlwords.infomine.com/xmlwords.htm

Philosophy

• Dictionary of Philosophical Terms and Names
  www.philosophypages.com/dy/

Social Sciences:

• Online Dictionary of the Social Sciences (Athabaska University)
  bitbucket.icaap.org/