See also: Analog Set-Top Box, Digital Set-Top Box
CIMM DEFINITION: A device that can be an actual box attached to the television externally or it can reside within the television. The Set-Top Box can be analog or digital, based on the quality and the signal and the technological capabilities of the box software.

2: A Set-Top Box is a device that enables a television set to become a user interface to the Internet and also enables a television set to receive and decode digital television (DTV) broadcasts. DTV Set-Top Boxes are sometimes called receivers. In the Internet realm, a Set-Top Box is really a specialized computer that can “talk to” the Internet – that is, it contains a Web browser (which is really a Hypertext Transfer Protocol client) and the Internet’s main program, TCP / IP. The service to which the Set-Top Box is attached may be through a telephone line as, for example, with WebTV, or through a cable TV company like TCI. In DTV, a typical digital Set-Top Box contains one or more microprocessors for running the operating system. A Set-Top Box also includes RAM, an MPEG decoder chip, and more chips for audio decoding and processing. More sophisticated Set-Top Boxes contain a hard drive for storing recorded television broadcasts, for downloaded software, and for other applications provided by your DTV service provider. (Source: itvdictionary.com and Searchnetworking.techtarget.com)

3: Any device that connects to a television set and an external source of digital or analog signal, converting the signal into content which is then displayed on the television screen, Also known as a converter box or video access device (VAD). (Source: Nielsen)

4: A cable Set-Top Box is a device that is an actual customer premises equipment that received television and other data signals through Cable, processes the signal, and outputs to the television. Majority of US cable Set-Top Boxes are manufactured by Motorola and Cisco / Scientific-Atlanta.(Source: FourthWall Media)

5: A device electronic device that connects to a TV providing connectivity to the Internet, game systems, or cable systems. (Source: IAB)

6: A physical device attached externally to a television, or resident internally, which when connected to an external source of digital or analog signal enables the display of video content on the television screen. (Source: MRC)