CIS
n. uncountablen. Stands for Commonwealth of Independent States. A group of countries that used to be part of the Soviet Union. They work together on things like trade and security.
n. Abbreviation for Commonwealth of Independent States. A regional intergovernmental organisation formed following the dissolution of the Soviet Union to facilitate cooperation in economic, political, and military affairs.
The CIS countries met to discuss new trade rules.
Several member states within the CIS have established a free trade area to simplify cross-border commerce.
The formation of the CIS served as a diplomatic mechanism to manage the transition of former Soviet republics into independent sovereign states while maintaining essential infrastructure links.
Initialisms.
Likely originates from the false etymology asserting that cis is an initialism standing for comfortable in skin.
Usually takes the definite article ('the CIS') and is treated as a singular entity.