A term used by some to describe people who are not transgender. “Cis-” is a Latin prefix meaning “on the same side as,” and is therefore an antonym of “trans-.” A more widely understood way to describe people who are not transgender is simply to say non-transgender people.
[According to the NLGJA Stylebook Supplement on Lesbian, Gay, Bisexual, & Transgender Terminology, cisgender “may be shortened to cis or combined as ciswoman or cisman. The word cisgender distinguishes without assuming that cisgender is the neutral or normal state.”]
REFERENCE: GLAAD Media Reference Guide – 10th Edition