"dubstep (n., 2002): a type of electronic dance music having prominent bass lines and syncopated drum patterns."
The inclusion of dubstep in this year's dictionary shows how influential the genre has become in the United States. Dubstep was born in England; however, Skrillex, Datsik, Excision, and other North American producers helped popularize the brostep sound. This aggressive offshoot of dubstep spread like wildfire among US college campuses a few years ago.
In addition to dubstep, Merriam-Webster added the following notable words to the dictionary: Auto-Tune, catfish, hashtag, selfie, social networking, and unfriend.