Typically used in terms like cisgender or cissexual. Cisgender people are those who remain their gender observed at birth by the doctor, cissexual refers to people who are attracted to those who are their birth gender. Can also be used as an acronym like "Comfortable In Self" which can imply those who are choosing a different gender than at birth (transgender) aren't comfortable with their existing self prior to transitioning which is true given gender dysphoria as a mental illness.
This guy is cis, he was born a male and chose to remain a male rather than transition to another gender.
by thepcwiz101 March 11, 2024
Get the cismug. by Catedrast December 10, 2024
Get the cis womanmug. by coveted seed July 24, 2023
Get the Cismug. 
#1 BH clan in RuneScape. Even though RoT flames all day long and have 100 people to their pk trips, they can't do anything but sit on their computer and cry.
by {`-`} April 15, 2008
Get the Team-CImug. A derogatory insult commonly used by the mentally disturbed, irate cross-dressers; to describe the sane individuals among us that happen to have an accurate understanding of human biology. Typically used by those who wish to be the opposite sex but cannot call themselves completely said gender, so they use this term to describe REAL members of whichever sex they wish to appropriate.
by basedbitchX July 16, 2023
Get the Cismug.