Cisgender

Definitions and Usage
Cisgender (often shortened to just 'cis') is used to describe the concept of identifying with one's Assigned Gender at Birth (AGAB). Cisgender is distinct from transgender, but the two terms are not necessarily mutually exclusive. Some nonbinary people identify as both trans and cis, or as neither. For example, an Assigned Female at Birth (AFAB) demigirl may identify partially as cis. Cis people, like trans people, can use any pronouns and present in any way regardless of AGAB or gender identity.

Flags
Cisgender has no flag and likely never will as it is not considered a part of the LGBT+ community.