Definition of Electronic Word-of-Mouth

The most well-defined and extensive definition of electronic word-of-mouth (eWOM) to date is by Hennig-Thurau, Qwinner, Walsh and Gremler (2004), who define the complex term as follows:

"Any positive or negative statement made by potential, actual, or former customers about a product or company, which is made available to a multitude of people and institutions via the Internet."

Source:
Hennig-Thurau, T., Qwinner, K.P., Walsh, G., Gremler, D.D. (2004), "Electronic word-of-mouth via consumer-opinion platforms: what motivates consumers to articulate themselves on the Internet?", Journal of Interactive Marketing, Vol. 18 No.1, pp.38-52.