поповщина

Etymology 1
Named after its leader Fedor Popov.

Noun

 * 1)  a guerilla movement on both sides of the middle part of Volga river and along the whole Medveditsa river. The movement was active during the Russian Civil War from February to Mai 1921.

Etymology 2
From

Noun

 * 1)  the Old Believer communities who recognize any form of ordained priesthood. See.

Usage notes
Both meanings are usually uncountable.