Any form of substance used as a filler to fill gaps, cracks, holes or spaces that need to be filled. These fillers can be professional fillers used in automotive body repairs, building fillers and cement or even rough mixtures lending themselves to be pushed and manipulated into the area to be filled up.
Derived from "Go Between"
"Get some gobo on that panel so it is ready for sanding in the morning"
"Shove some gobo in it, that should do the trick"
"Get some gobo mixed up ready for building this wall"