appropriation

Appropriation is the process of using or adapting a general product or service so that it serves a purpose for the user that was not envisaged by the designer or explicitly designed into the system. For example, one might use the address field in a phone contacts list to keep track of what books they have borrowed from you.

While the exact form of appropriation is, by definition, not envisaged by the designer; it is possible to design for appropriation, making it easier for users to create their own appropriations.