I am taking a writing class, and my professor spent 10 plus minutes extolling the virtues of a good bound dictionary. He named quite a few user interface features that satisfied his requirements more completely in a book. However, I don't desire to limit this question to the bound copy.
He went on to dismiss many online editions due to the editorial decisions of the free dictionaries online. He listed missing etymologies, shorter definitions, less examples and fewer esoteric definitions.
Regardless, writing often is listed on job descriptions as being very important, and we all know if there is any documentation, it would be nice if it were written well. Further presuming a dictionary is a good tool to facilitate ones writing; what resource(s) do you draw upon to figure out what that word means?