directional drilling (di-rec'-tion-al). The intentional drilling of a well at controlled departures from the vertical and at controlled azimuths, often utilizing a whipstock or a special downhole assembly with a bent (angled) subassembly and a turbine motor located close to the drill bit. It is done to establish multiple wells from a single location such as an offshore platform, and for other purposes. Cf: deviation [drill]; sidetracking.