"Expand to include more stringent criteria for higher quality" certainly sounds like "bigger and more robust" to me.
Here are a couple of examples that come to mind:
On one project we went several iterations without any persistence. Once we implemented persistence, all future stories were expected to include persistence and all releases were expected to support upgrading existing data.
Similarly with internationalization. Don't worry about it for several iterations, then implement it by externalizing all our user-visible strings, then expect all user-visible strings to be externalized as part of all future stories.
Are those examples of a definition of done getting more mature, or bigger, or more robust? Or do you not consider them included in a definition of done?