I think he's referring to the definition of ambition Quirrel uses in Chapter 70:
The Defense Professor's fingers idly spun the button, turning it over and over. "Then again, only a very few folk ever do anything interesting with their lives. What does it matter to you if they are mostly witches or mostly wizards, so long as you are not among them? And I suspect you will not be among them, Miss Davis; for although you are ambitious, you have no ambition."
I guess it depends on what one finds interesting. Clearly QQ/LV found taking over Magical Britain interesting enough.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 122, which is the final chapter of the story.
Happy once-in-a-century Pi Day! (3/14/15 == 3.1415)
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)