"Hydraulic lines" refers to the pipes or tubes that carry fluids, usually oil or water, in a hydraulic system. These lines enable the transmission of force and energy to power various machinery and equipment. Full definition
When removing an anti-lock brake system controller, there are many brake hydraulic lines connecting to it; Usually there are between eleven to fifteen lines connected to the ABS controller. (yourmechanic.com)
The same hydraulic lines minimize body roll in cornering and do it so well the car doesn't even have an anti-roll bar. (extremetech.com)
This avoided running hydraulic lines from the engine (which was behind the driver in the MR2) up to the steering rack. (en.wikipedia.org)