I've known Wordnik for a while, but never realized it wasn't on Product Hunt yet. I'm actually using it these days for writing an essay, and I find it so useful to search for related words, definitions, and examples that you can even see and hear. You can also contribute to the community by discussing on words and organizing them into lists. It's so powerful, check it out!
P.S. there is also an API for the devs out there ;)
