An ASCII  text file in the PostScript language. PostScript is a page description language, and has become an industry standard for printing high quality text and graphics. There are PGPLOT  device drivers which can create a PostScript file. This file can be sent to a printer to get hardcopy output.

a description, in the PostScript language, of a graphic image or pages

a file created by printing a document to a file, using a PostScript printer driver

a high-level, device-independent way of representing page images