First defined on xkcd.
2. Doing the thing above in a situation where the obsession may lead to bodily harm (in the original context on the middle of a road where they will get inevitably run-over by a truck).
2. There's a certain type of brain that is easily disabled. If you show it an interesting problem it involuntarily drops everything else. This lead me to the development of a new sport: Nerd Sniping.