Online translations can be dodgy. In fact, I wouldn’t recommend it. Even trying to find the meaning of a foreign word online can be difficult, depending on what site you go to. If you come across a verb you don’t know (and don’t realise it’s a verb), you might type it in all unconjugated and goodness knows what you get back, if anything.
I’m sure there are quite a few good references for the popular european languages, though. I’m just recommending one I have found, which works quite well – WordReference.com. Their main dictionary languages are French, Italian, Spanish, German and Russian, but they do seem to have support for further languages. I have mainly used it for the romance languages.
When it comes to the languages with different alphabets, you may have a problem. With Greek and Russian, you could still go the long, painful route of ‘inserting characters’ in MS Word and the copy-pasting to your browser, but what about Korean and Japanese? I really would not know.
However, what I have seen of this site, from my use of it with Italian & French, is pretty impressive. It knows a conjugation when it sees one, and can generally provide you with a conjugation table for the verb. It also gives many usages of a word in context. So, as far as I’m concerned, this is a solid, useable online dictionary that won’t leave you more confused than when you started.