A foreline is a vacuum line between the pumps of a multistage vacuum system. 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. A classic foreline is a hose or tube that connects a rotary vane pump to the outlet of an oil diffusion pump, although vacuum technology now uses a vast array of roughing pumps and high vacuum pumps.
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.
References
Foreline Wikipedia(Text) CC BY-SA