The Disjunction Drive is a space drive that depends on the idea that the source of a field and that which the field acts on can be separated, or that a field can be created separated (or "disjoint") from its source. By the source and reactant in space, the reactant is shifted to a point where the field has a slope, thus producing reaction forces between the source and the reactant.
The common science-fiction idea of a gravity drive that creates a gravity well in front of the ship which moves with the ship as it continuously falls into the well is a Disjunction Drive. However, as with the Diametric Drive, gravity is not the only force that could be employed in this form of space drive.
Current evidence indicates that the source, reactant, and inertial mass properties are inseparable, making a Disjunction Drive impossible. The best hope for a Disjunction Drive is the idea that a source or reactant mass could be mimicked / simulated by some coupling between gravity and electromagnetism or some other form of controlling gravity that would allow the arbitrary warping of spacetime into artificial gravity wells.
An illustration of the space-time distortions generated by a Disjunction Drive can be found at http://www.geosoc.org/schools/adult/docs/Image29.gif
Information on space drives: http://www.grc.nasa.gov/WWW/PAO/html/warp/ideachev.htm