The stencil duplicator or mimeograph machine (often abbreviated to mimeo) is a low-cost printing

Printing

Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....

 press that works by forcing ink through a stencil onto paper.

Along with spirit duplicator

Spirit duplicator

A spirit duplicator was a low-volume printing method used mainly by schools and churches. It was also used by members of science fiction fandom and early comic book fandom to produce fanzines...

s and hectograph

Hectograph

The hectograph or gelatin duplicator or jellygraph is a printing process which involves transfer of an original, prepared with special inks, to a pan of gelatin or a gelatin pad pulled tight on a metal frame.-Process:...

s, mimeographs were for many decades used to print short-run office work, classroom materials, and church bulletins. They also were critical to the development of early fanzines because their low cost and availability enabled publication of amateur writings.