Dictionaries are harmful(Potentially relevant link)
Dictionaries give definitions of words. That's bad. Probably worse than dictionaries are 'Word of the Day' things.
I have no good way of explaining what the heck I'm talking about, but one example I've come across is 'appease'. Some silly person I know learned the word not by seeing it in use a thousand times, but by coming across it once and asking for/looking up the definition.
Now she uses the word. Based on the definition.
Like most words, 'appease' has connotations and tendencies of usage that a dictionary cannot capture with a simple definition and a single example sentence. So I'll be reading something written by aforementioned friend and suddenly I'll be verbally slapped in the face by the word 'appease' being used in a manner that just grates the mind.
Now, I'm all for words being used in unusual ways, but only if they fit. Being the belegwain ned Amar, the first example that comes to my mind is Legolas commenting 'Unless my eyes are cheated...' That's not the typical usage of 'cheated', but it perfectly suits the context.
The next time you're wondering what a word means, rather than pulling out a dictionary, try reading through a few hundred examples (better search terms welcome). Sure it might take you a couple hours for each new word, but it's well worth it.