Abbreviation for nonaqueous phase liquid. This term is used to describe the physico- chemical that exist between a bulk hydrocarbon and water which results in the two liquids being immiscible with one another (i.e. little or no mixing of the two liquids occurs.) The interface is a physical dividing surface between the bulk phases of the two liquids. NAPLs are divided into two categories; LNAPLs and DNAPLs. See also DNAPL; immiscible; LNAPL.