Officially launched last week, dictionary site Vocabulary.com offers definitions and pronunciations for each of the 150,000 words in The World’s Fastest Dictionary. Many words also have a plain English, sometimes sassy explanation and real-world usage examples. From a word’s definition page, you can add the word to one of your word lists, include it in your Challenge like it on Facebook, and look up its synonyms on Visual Thesaurus. Not all functions are available yet for all words.

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