derrick, apparatus with a tackle rigged at the end of a beam for hoisting and lowering. Its name is derived from that of a famous early 17th-century hangman of Tyburn, Eng. In the petroleum industry, a derrick consisting of a framework or tower of wood or steel is erected over the deep drill holes of oil wells to support the tackle for boring, to raise and lower the drilling tools in the well, and to insert and remove the well casing or pipe. Similar smaller structures mounted on trucks are also called derricks. The derrick is a type of crane (q.v.).