Abbreviated form of Junior Common Room (more commonly used than the full version) in UK universities and their halls of residence - usually just a students' TV lounge, occasionally a bar, maybe a pool table or two - and by extension to the elected body responsible for apologising to the cleaners, paying the cable bill and getting some dodgy tabloid delivered every Sunday, and, by even more extension, to the entire undergraduate student body for the college or hall in question. In collegiate institutions it is often complemented by a Middle Common Room (for postgraduate students) and a Senior Common Room (a rather more well-appointed club for academic staff), but they don't get abbreviated so frequently.