Online Dictionaries

Online Print Dictionaries

These are dictionaries that also have a version in print. These definitions may be better if you actually need to cite them.

• American Hertiage Dictionary
• Merriam Webster - Merriam Webster is a reliable source, but there are some words that not available free of charge.

Compiles multiple sources

These dictionaries that do not necessarily have their own database of word. Instead, they compile information from several different sources.

• Dictionary.com - An excellent resource that has definitions from trusted online sources and print sources
• Google - You can use define:wordtodefine to look up words with Google.

Miscellaneous Dictionaries

• Definr - A dictionary that has many methods of quick access.
• Free Dictionary
• Wiktionary - A collaborative wiki style dictionary. Other information besides the definition is often available here, such as the etymology of words.

Topic Specific Dictionaries

These dictionaries specialize in a specific topic. They often contain words in their field that you may not be able to find definitions for in generic dictionaries.

• Acyronym Finder - A dictionary of all acronyms and abbreviations.
• Dictionary of Algorithms and Data Structures
• Online Etymology Dictionary
• Free On-Line Dictionary of Computing - A dictionary dedicated to all things computer and technology related.
• Geography Dictionary and Glossary
• Urban Dictionary - A user maintained dictionary of slang terms.

Language Tools

• howjsay.com - A quick "speaking" dictionary. It doesn't have definitions, but only has a sound clip of how to pronouce about every word you can think of.