Paint thinner
A paint thinner is a solvent used to thin (i.e. make it less thick) paints or varnish. Paint thinners are diluents. Solvents labeled "paint thinner" are usually white or mineral spirits.
Certain organic solvents used as paint thinners on painting materials can be harmful in of themselves, as well as through the release of hazard substances, including lead and other additives from dissolved paint stuffs.