thinner
n. C / Un. a liquid you mix with paint to make it less thick. It is also useful for cleaning paint off brushes and tools.
n. a volatile solvent used to reduce the viscosity of paints, varnishes, or lacquers to facilitate application. Often used as a cleaning agent for equipment after use.
Add a little thinner to the paint so it flows better.
The artist used a small amount of paint thinner to clean the oil residue from her brushes before they dried.
Industrial-grade thinner must be handled with care in well-ventilated areas due to the high concentration of volatile organic compounds that can cause respiratory irritation.
From thin + -er.
Uncountable when referring to the substance in general; countable when referring to specific types or containers of the liquid.