Plain English Meaning
Fuel lines that come from the manufacturer already shaped and finished, so the pilot or owner can swap an old one out for a new one without having to build the line from raw tubing.
Full Definition
Fuel lines that have been manufactured in advance to a specific shape, length, and fitting configuration for a particular aircraft installation, supplied ready to install without on-site bending, cutting, or fitting fabrication. Replacing prefabricated fuel lines is one of the preventive maintenance tasks a certificated pilot may perform on their own aircraft under 14 CFR Part 43, Appendix A.
Context Anchor
Seen in the Federal Aviation Administration list of preventive maintenance tasks that an eligible pilot or owner may perform on an aircraft.