noun - CIS refers to an acronym for the Commonwealth of Independent States, a regional intergovernmental organization of nine members and two founding observer members, all being former Soviet Republics located in Eurasia.

noun - In chemistry, CIS represents a certain configuration in which two atoms or groups of atoms are on the same side of a given plane.

noun - In gender studies, CIS or cisgender refers to a person whose gender identity matches the sex assigned to them at birth.