Wiktionary
alt. 1 (context roofing English) Sheet material, such as reinforced kraft paper, rosin-sized paper, polyester scrim or polyethylene sheeting, placed between two components of a roof assembly to ensure that no adhesion occurs between them and to prevent possible damage from chemical incompatibility, wearing or abrasion of the membrane. 2 (context shipping English) A strong, thin pallet-sized sheet of plastic or fiberboard used to transport heavy items. n. 1 (context roofing English) Sheet material, such as reinforced kraft paper, rosin-sized paper, polyester scrim or polyethylene sheeting, placed between two components of a roof assembly to ensure that no adhesion occurs between them and to prevent possible damage from chemical incompatibility, wearing or abrasion of the membrane. 2 (context shipping English) A strong, thin pallet-sized sheet of plastic or fiberboard used to transport heavy items.
Wikipedia
Slip sheets are thin pallet-sized sheets made of plastic, heavy laminated kraft paperboard, or corrugated fiberboard used in commercial shipping. Often, these replace the use of traditional wooden pallets. The unit load is usually stretch wrapped or shrink wrapped for stability.