What is Raster Image Processor?

Legal Definition
A raster image processor (RIP) is a component used in a printing system which produces a raster image also known as a bitmap. Such a bitmap is used by a later stage of the printing system to produce the printed output. The input may be a page description in a high-level page description language such as PostScript, Portable Document Format, XPS or another bitmap of higher or lower resolution than the output device. In the latter case, the RIP applies either smoothing or interpolation algorithms to the input bitmap to generate the output bitmap.

Originally RIPs were a rack of electronic hardware which received the page description via some interface (e.g. RS-232) and generated a "hardware bitmap output" which was used to enable or disable each pixel on a real-time output device such as an optical film recorder.

A RIP can be implemented either as a software component of an operating system or as a firmware program executed on a microprocessor inside a printer, though for high-end typesetting, standalone hardware RIPs are sometimes used. Ghostscript and GhostPCL are examples of software RIPs. Every PostScript printer contains a RIP in its firmware.

Earlier RIPs retained backward compatibility with photosetters so they supported the older languages. So, for example Linotype RIPs supported CORA (RIP30).
-- Wikipedia
Legal Definition
A device that will translate vector images into images that can be printed by dot matrix printers, laser printers and recognised by scanning equipment. It will produce a bitmap of an image. A piece of hardware and not software hat is located between the computer and the printer.