The Russian Chimney Sweep is the act of the female taking a dump, while her partner is performing anal sex. It is called the Russian Chimney Sweep, because it's origin is in Russia, and the asswhole is being cleaned out, like a chimney.
Chick: I gotta take a dump.
Guy: I want to have anal sex.
Chick: Want to do the Russian Chimney Sweep? My chimney needs some sweeping.
Guy: Let's get cleaning.