The term 'Surfacing Goop' is a type of adhesive material used in construction and repair projects. It is made up of TAR, which is a dark, viscous liquid or semi-solid form of petroleum. TAR is often used as a sealant or waterproofing agent, and is also used in road construction and roofing. Surfacing Goop is a combination of TAR and other materials, such as sand, gravel, and asphalt, that is used to fill in cracks and gaps in surfaces. It is a versatile material that can be used for a variety of applications, including sealing and waterproofing.