OCLC's definition – Ch. 9 (7)
An electronic resource is a manifestation of a work encoded for manipulation by computer. The manifestation resides in a carrier accessed either directly or remotely. Some electronic resources may require the use of a peripheral device attached to a computer (for example a CD-ROM player). The definition does not include electronic resources that do not require the use of a computer, for example, music compact discs and videodiscs.