Merriam-Webster

Ohodnoceno 4 z 5 hvězdiček

od Leobinus dne Kvě. 18, 2008 · trvalý odkaz

I've used M-W for years, and haven't seen any alternative that I preferred. I subtracted a star because there are some words that you have to pay a fee to see, but those words are uncommon. The audio pronunciations are a great addition, too.