tedster - 3:07 am on Jul 27, 2010 (gmt 0)
Google's blog "This Week in Search" featured information about a change in how and when definitions are triggered. Nothing about the four small links, but they do mention some new functionality that they call "implicit triggereing":
We added implicit triggering, which means you can simply search for [flummox] and find the definition, you don't have to search for [define flummox] or [what is flummox]. We've also improved the definition result snippet to show more details such as parts of speech and pronunciation.