Salvage Parts: Parts that have been harvested from donor vehicles in salvage yards, or from a totaled vehicle. They may be an OE part or imitation part.
For more information on salvage parts.
Sanding: An abrasive process used to level a coated surface prior to the application of a subsequent further coat. (Also see Grinding)
Sealer: An undercoat which improves the adhesion of the topcoat, and which seals old painted surfaces to prevent bleed-through.
Select Repair Shop: Collision repair shops that participate in one or more insurance company DRP programs. Vehicle owners have the right to choose a body shop whether it is part of a DRP program or not.
Solid Color: A coating which contains only colored pigments, as opposed to a coating which contain small metallic flakes to create metallic paints.
Solvent: A liquid, usually volatile, which is used to reduce paint or primer viscosity. Solvents evaporate during application and drying of paint and therefore do not become a part of the dried film. 
Steering: Any attempt by an insurer to get the consumer to take their vehicle to a shop not of their own choosing. Steering is illegal in most states. Vehicle owners have the right to have their vehicle repaired at a shop of their choosing.
Subrogation: Refers to circumstances (such as when another party is responsible for an accident) in which your insurance company has paid expenses for medical and vehicle repair and then tries to recoup the expenses it paid from the other party or their insurance company. 
Substrate: The uncoated/unpainted body panel surface.
Supplement: Additional repairs needed to complete the repair that were not identified on the original estimate. It is often impossible to identify all damage to a vehicle until it's disassembled.
Surcharge: An increase in your auto insurance premium due to an at-fault accident or a moving violation.