Some of the dictionaries available under the category "Collegiate Dictionaries":
American Heritage Dictionary of the English Language, 4th EditionMerriam-Webster's Collegiate Dictionary, 11th EditionWebster's New World College Dictionary, 4th EditionCollins English Dictionary, 8th EditionWebster's Third New International Dictionary of the English Language, UnabridgedOxford English DictionaryWordNet 3.0Babylon English Dictionary
American Heritage Dictionary of the English Language, 4th Edition





Merriam-Webster's Collegiate Dictionary, 11th Edition



Webster's New World College Dictionary, 4th Edition

Collins English Dictionary, 8th Edition



Webster's Third New International Dictionary of the English Language, Unabridged



Oxford English Dictionary


WordNet 3.0


Babylon English Dictionary