Longman Dictionary of Contemporary English Online

This has got to be one of the best monolingual online dictionaries for learners. I have added it to my Killer Links, so if I use any "big words" you can just look them up.

As far as I can tell, the link below takes you to the actual search page where you can look up words

http://pewebdic2.cw.idm.fr/

and

http://www.ldoceonline.com/

takes you to the homepage and you have to click again to get to the actual dictionary.

If you haven't got such a dictionary in paper and the CD-ROM that comes with it , then you really should get it. It's not even expensive! Costs less than 15€ at the English Bookshop in Graz.

There is a more expensive edition which pronounces not just the words but the example sentences as well. Description below:

NEW – Updated Edition of the Longman Dictionary of Contemporary English 4th
Edition. For advanced learners of English. Your link to living language. 155,000
natural examples bring English to life. British and American pronunciations of
headwords, including people and place names. New: 88,000 spoken example
sentences pronounced on the CD-ROM. 1 million additional sentences from books
and newspapers. 3000 most frequent words in spoken and written English
highlighted. 4000 new words and meanings. 23x15 cm, illustrated, 1950 pages.