Commonwealth of Independent States; putative successor to the USSR, except that the Baltic Republics of Estonia, Latvia, and Lithuania never joined. Contrary to another definition of CIS at the Urban Dictionary, the CIS does not stand for "Communist Independent States." Moreover, that definition has the CIS existing BEFORE 1991, and includes Kazakhstan as "not officially part of the Soviet Union." Kazakhstan was, in fact, one of the 15 republics of the USSR until 1991.
The CIS came into being December 1991. Mostly consists of regularly scheduled conferences of foreign ministers and defense ministers.
In 1995, members Belarus and Russia created the Commonwealth of Sovereign Republics (CSR
The August 2008 war between Georgia and Russia was unique in being a direct war between CIS member states, although there have been others waged by proxy.