The Collins English Dictionary is now free online. Comprehensive English dictionary, thesaurus, usage examples, synonyms, translations, word trends and images. Also includes Collins best-selling French, German and Spanish dictionaries.
This beginner's dictionary features 1500 "key" words in the English language, needed to survive in an English speaking locale. BED is a free site featuring key English words with simple definitions and sample sentences. In addition, we have an ever-growing content section containing original comics and idioms,etc.
Wiktionary is the lexical companion to the popular open-content encyclopedia Wikipedia.
Wiktionary is a collaborative project to produce a free, multilingual dictionary of all words in all languages, with definitions, etymologies, pronunciations, sample quotations, synonyms, antonyms, translations, thesaurus etc.