Dictionaries are fantastic resources, but they are human and they are not timeless. I'm struck as a teacher that we tell students to critically question every text they read, every website they visit, except dictionaries, which we tend to treat as unauthored. As if they came from nowhere to give us answers about what words really mean.
Here's the thing: if you ask dictionaries editors, what they'll tell you is that they're just trying to keep up with us as we change the language.
Anne Curzan has given a fantastic TED talk on what what makes a word real. In it, she discusses our somewhat conflicted relationship with dictionaries.
I've mentioned before that I consider myself a descriptivist. What I love about Anne Curzan's talk is her point that you can strongly dislike a word, but still accept it's usage in a living and ever-changing language.