noun. A painful predicament, when literal, for the ass-owner. In the metaphorical cases, pain is well-distributed amongst friends and countrymen.
Real citation: "Even taking into account the licensing difficulties I suspect that it could have been stated more clearly. And then there's the whole _Lungbarrow_ problem that's brought up by the use of "brother" rather than "I have a, well, the relationship is something like a brother," which would at least have left open the possibility that Irving was a Cousin who avoided being namechecked during _Lungbarrow_ and later managed to overcome the family trait of iron-rod-up-one's-assedness and chose to hit the road."
(William December Starr, Nov. 9, 2001, http://groups-beta.google.com/group/rec.arts.drwho/msg/85f5ed3ea546c88f)
Made-up citation: "Like diabetes, alcoholism, and flying-squirrel ownership, iron-rod-up-one's-assedness is hereditary. It can only be overcome through sugar, alcohol, and adorable exotic pets."