Lapizuli - 9:22 pm on Nov 7, 2010 (gmt 0)
Regarding the definition of bounce rate in Google Analytics, I'd read a detailed definition recently, but couldn't find it again. This is the closest thing I found from Google's own mouth - it's one of those things you have to piece together with definitions in different places. Combine it with the quote from Sgt_Kickaxe:
The percentage of single-page visits (i.e. visits in which the person left your site from the entrance page).
The number of times your visitors have been to your site (unique sessions initiated by all your visitors). If a user is inactive on your site for 30 minutes or more, any future activity will be attributed to a new session. Users who leave your site and return within 30 minutes will be counted as part of the original session.
This field identifies the number of single-page visits to your site over the selected dimension.