Frequently cited MC definitions

Tseng, M.M. / Jiao, J. (2001): Mass Customization, in G. Salvendy (Ed.) Handbook of Industrial Engineering, 3rd edition, New York: Wiley, p. 684-709
The objective of mass customization is "to deliver goods and services that meet individual customers' needs with near mass production efficiency.

Kaplan, A.M. / Haenlein, M. (2006): Toward a parsimonious definition of traditional and electronic mass customization, Journal of Product Innovation Management, 23(2), pp. 168-182.
... a strategy that creates value by some form of company-customer interaction at the fabrication / assembly stage of the operations level to create customized products with production cost and monetary price similar to those of mass-produced products.

Davis, S. (1987): Future perfect, Reading, MA: Addison-Wesly, p. 169
Mass Customization of markets mean that the same large number of customers can be reached as in mass markets of the industrial economy, and simultaneously they can be treated individually as in the customized markets of pre-industrial economies.

Tseng, M.M. / Piller, F. (2003): The customer centric Enterprise. Advances in Mass Customization and Personalization, Munich, p. 247
Mass Customization aims at providing cost-effective products and services to meet individual customer's needs. An implicit assumption of mass customization is that organizations must recognize customers as individuals and understand their needs.

Mass Customization refers to a customer co-design process of products and services which meet the needs of each individual customer with regard to certain product features. All operations are performed within a fixed solution space characterized by stable but still flexible and responsive processes. As a result, the costs associated with customization allow for a price level that does not imply a switch in an upper market segment.

For a full Mass Customization definition by Frank Piller, please click here

For an even more extensive view on the topic see the in-depth discussion of the definition of mass customization.