A printmaking technique developed in the 17th century that allows for the creation of prints with soft gradations of tone without the use of hatching. A copper or steel plate is first worked all over with a serrated tool called a rocker, raising burrs over the surface to hold the ink. The design is then created in lighter tones by scraping out and burnishing areas of the roughened plate so that they hold less ink (or none in the highlights). The mezzotint technique was used widely as a reproductive printing process, especially in England, until photographic processes overtook it in the mid-19th century. Web resource here.
George Stubbs. Sleeping Cheetah (“A Tyger”). Mezzotint. 1788. Princeton University Art Museum, Princeton, N.J.