An airbrush is a small, air-operated

Pneumatics

Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...

 tool that sprays various media including ink

Ink

Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

 and dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

, but most often paint

Paint

Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 by a process of nebulization. Spray guns

Spray painting

Spray painting is a painting technique where a device sprays a coating through the air onto a surface. The most common types employ compressed gas—usually air—to atomize and direct the paint particles. Spray guns evolved from airbrushes, and the two are usually distinguished by their size and the...

 developed from the airbrush and are still considered a type of airbrush.
The first airbrush, depending on your definition, was patented in 1876 (Patent Number 182,389) by Francis Edgar Stanley

Francis Edgar Stanley

Francis Edgar Stanley was an American businessman and was the co-founder, along with his twin brother Freelan Oscar Stanley, of the Stanley Motor Carriage Company which built the Stanley Steamer.-Biography:...

 of Newton, Massachusetts

Newton, Massachusetts

Newton is a city in Middlesex County, Massachusetts, United States bordered to the east by Boston. According to the 2010 U.S. Census, the population of Newton was 85,146, making it the eleventh largest city in the state.-Villages:...

. Stanley and his twin brother later invented a process for continuously coating photographic plates (Stanley Dry Plate Company) but are perhaps best known for their Stanley Steamer

Stanley Steamer

The Stanley Motor Carriage Company was a manufacturer of steam-engine vehicles; it operated from 1902 to 1924. The cars made by the company were colloquially called Stanley Steamers, although several different models were produced.-Early history:...

.