Foreline
A foreline is a vacuum line between the pumps of a vacuum system. A pump which takes gas out of a foreline is known as a backing pump.
A classic example of a foreline is the hose or tube that connects a rotary vane pump to the of an oil diffusion pump. The rotary vane pump functions as a backing pump. Many other examples exist, since vacuum technology now uses a vast array of roughing pumps and high vacuum pumps. No longer exclusively used by scientists in research, vacuum systems are used in numerous industries that include food production and the manufacturing of electronic components.
Although the term has been used for many decades in the high vacuum system industry and in literature concerning vacuum systems, the word foreline has not yet been added to any dictionary.