WordWeb is a complete English dictionary, simple and free, allowing you to look up definitions and synonyms with no need to have an Internet connection. But it also offers the possibility of running searches on the free encyclopaedia Wikipedia and other online dictionaries.
WordWeb is a very complete dictionary. It has everything you need to easily obtain a fast reference of the searched words. It includes definitions and synonyms, property of the nouns, antonyms, related words, pronunciation, etc.
WordWeb has an ample database (about 150,000 words and 120,000 synonyms), however, these numbers increase considerably as you use the online dictionary.