Merriam Webster's Collegiate Dictionary Updated annually with more than 10,000 new words and phrases and 40,000 usage examples, along with 165,000 entries and 225,000 definitions. (all full text)
Oxford English Dictionary An historical dictionary of the English language tracing through 2.5 million quotations from a wide range of sources the usages, variant spellings, pronunciations and senses of more than half a million words. Updated quarterly. (all full text)