The canonical hypothetical mechanism by which critical knowledge is lost from a team through unexpected personnel attrition.
This definition is of less importance than simply the knowledge that it is bad. If you have a BusSensitive team or project, go look at BusNumber and how to increase it; the directions there are more to the point.
I can't believe we've talked around this concept in a bunch of different pages without pointing at the actual term. Go YAGNI, I guess. I'm not sure how much anecdotal prattling this wiki encourages, but if somebody asks, I'll relate the bus story of the developer on my team who FellAsleepHiking?. -- DavidBradyNow I'm curious.