Liner
Liner means a continuous layer of natural or man-made materials, beneath or on the sides of a surface impoundment, landfill, or landfill cell, which restricts the downward or lateral escape of hazardous waste, hazardous waste constituents, or leachate.
Source
40 CFR § 260.10
Scoping language
When used in parts 260 through 273 of this chapter, the following terms have the meanings given below: