Dubdrop
A dubdrop is the bass drop of a dubstep song, to which the rest of the song builds. The drop is typically characterized by a measure or so of reduced intensity in the music followed by an explosive entry of sub-bass and bass on the downbeat of the next measure. The nearly ubiquitous inclusion of very prominent sub-bass separates dubdrops from house drops or trance drops. Some dubstep songs might build up twice to the same drop such as Crizzly's remix of Willow Smith's "I Whip my Hair." Some songs feature an initial dubdrop and then proceed to build to a second one in halftime. These halftime drops can often be more moving and dramatic than regular dubdrops and are becoming more frequently used as the genre progresses.
The dubdrop in that song cracked the walls of my house. I live in a bomb shelter...