Dubstep
The name "dubstep" was first used around 2002 by Ammunition Promotions, who ran the London night club Fwd (Forward) where the dubstep genre was first heard. They also managed several record labels that had dubstep releases.
Dubstep is a genre of electronic music who's origins date back to 1998, with releases by El-B, Oris Jay, Zed Bias, Steve Gurley, and others. It's less about lyric and vocals and more about the beat. The music is more often in a minor key with a shuffle feel at a tempo of around 138 to 142 beats per minute, but actually feels half that tempo, since the backbeat is on beat three as opposed to beats two and four.
The prime focus in dubstep is the bass, with a heavy sub-bass. Some dubstep tracks have what's called a wobble bass or "wub", where an LFO set to a multiple of the tempo of the song modulates certain synth parameters to alter the bass's timbre.
Dubstep drums usually play a syncopated shuffle beat. It also has sampled synth elements, almost no guitars, and is primarily instrumental with an occasional vocal texture. The harmonies are often dissonant, and the feel is extremely dark.
Dubstep grew out of many genres including 2-step garage, drum and bass, jungle, reggae, broken beat, techstep, and others that were popular in London at that time.