1. A Page Description Language that gets its leverage by using a full programming language, rather than a series of low-level escape sequences, to describe an image to be printed on a laser printer or other output device (in this it parallels EMACS, which exploited a similar insight about editing tasks). It is also noteworthy for implementing on-the fly rasterization, from Bezier curve descriptions, of high-quality fonts at low (e.g. 300 dpi) resolution. From Linux Guide @FirstLinux

2. A page description language developed by Adobe Systems that tells a printer how to display text or graphics on a printed page. From I-gloss

3. A sophisticated page description language (PDL) that's used for high-quality printing on laser printers and other high-resolution printing devices. Though Postscript is a programming language adn you can learn to write page descriptions in it, Postscript is usually invisible and automatic. Programs generate Postscript code that goes to the printer, where a Postscript interpreter follows the coded instructions to generate an image of the page precisely according to there instructions. A major benefit of Postscript is its device independence; you can print the Postscript code generated by an application on any printer with a Postscript interpreter. You can take Postscript files generated on your PC to a service bureaus which can print the document using expensive typesetting machines with resolutions of up to 2,400 dots per inch (dpi). See Postscript font, and Postscript printer. From QUECID

4. n. A Page Description Language (PDL), based on work originally done by John Gaffney at Evans and Sutherland in 1976, evolving through `JaM' (`John and Martin', Martin Newell) at XEROX PARC, and finally implemented in its current form by John Warnock et al. after he and Chuck Geschke founded Adobe Systems Incorporated in 1982. PostScript gets its leverage by using a full programming language, rather than a series of low-level escape sequences, to describe an image to be printed on a laser printer or other output device (in this it parallels EMACS, which exploited a similar insight about editing tasks). It is also noteworthy for implementing on-the fly rasterization, from Bezier curve descriptions, of high-quality fonts at low (e.g. 300 dpi) resolution (it was formerly believed that hand-tuned bitmap fonts were required for this task). Hackers consider PostScript to be among the most elegant hacks of all time, and the combination of technical merits and widespread availability has made PostScript the language of choice for graphical output. From Jargon Dictionary