It is from a previous life and there it means "Post Prandial Depression", which is what makes one want to fall asleep after a meal.
What do they call it when after looking at screen after screen of mass spectral data, you start to fall asleep? That's what was just happening to me. (But then is a bit after lunch too...)
Kirk
For up from the ashes, up from the ashes, grow the roses of success!