cleavage /klivd/ noun
1 [C, U] the space between a woman's breasts that can be seen above a dress that does not completely cover them
2 [C] (formal) a difference or division between people or groups: a deep cleavage between rich and poor in society (OALD)http://www1.oup.co.uk/elt/oald/bin/oald2.pl
"Da der Cleavage-Begriff in dieser Arbeit zentral ist, wird er an dieser Stelle kurz erläutert: Cleavages sind zentrale gesellschaftliche Konfliktlinien, entlang derer sich die Gruppeninteressen allmählich organisieren (vgl. Falter/Schoen 1999: 457 )" http://www.hausarbeiten.de/faecher/vorschau/2...
"Our point of departure is the theory of social cleavages set out by Seymour Martin Lipset and Stein Rokkan in 1967." (pdf) http://www.utdallas.edu/~cjwilson/prof/BJPS00.pdf
"Lipset and Rokkan suggest that there are three specific connotations to the term cleavage. First, a cleavage involves a social division that separates people along at least one key social characteristic such as occupation, status, religion or ethnicity. Second, groups involved in a cleavage must be conscious of their collective identity and be willing to act on that basis. Third, a cleavage must have an organizational component that gives formal institutional expression to the interests of those on one side of the division." http://homepages.udayton.edu/~aherndaw/clvages.htm
"Von der Rokkanschen Cleavage-Gesellschaft ..." http://www.politik.uni-trier.de/mitarbeiter/s...
This seems to have really caught on in Germany. I'd like to call upon all Germans *not* to use phrases such as "revealed a huge cleavage" when writing in English, however - see meaning 1 of the OALD, above. Mind you, it does give us proofreaders a good laugh.