Formal Definition of User-Centered Design
http://www.taskz.com/definitions.php

TaskZ

Abstract:

UCD is a highly structured, comprehensive product development methodology driven by: (1) clearly specified, task-oriented business objectives, and (2) recognition of user needs, limitations and preferences. Information collected using UCD analysis isscientifically applied in the design, testing, and implementation of products and services. When rigorously applied, a UCD approach meets both user needs and the business objectives of the sponsoring organization.