Steve Miller (President of Pragmatic Software) has defined Gold Plating the following way:
Gold Plating - Similar to scope and feature creep, programmers can also incur risk by making the feature more robust than is necessary. For example, the specification for the Logon page contained a screen shot that showed very few graphics, it was just a simple logon process. However, the programmer decides that it would be really cool to add a FLASH based movie on the page that fades in the names of all the programmers and a documentary on security. This new movie (while cool in the programmer's eyes), takes 4 hours of additional work, put their follow-on tasks are n jeopardy because they are now behind schedule. http://www.softwareplanner.com/Newsletters/newsletter_2004_07_SP.htm
Another Definition:
Adding more to the system than specified in the requirements. Gold plating is not a bargain. It can increase operation and maintenance costs and reduce quality. Gold plating indicates project processes are out of control. Gold plating can also be accomplished by adding unnecessary requirements. Risk adjusted cost-benefit analyses can help avoid this form of gold plating. \\.jiludwig.com/Definitions.html