See prefix cis-
A term meaning someone who has not crossed the boundaries of gender, by not exhibiting cross-gender behavior. One who lives and feels that their internal gender is the same as their physical sex. Or more often, does not conceive of themselves has having an internal gender, and would not have, and never had, second thoughts about their gender.
The term is almost exclusively used when discussing transgenderism and transgender issues to refer to the majority of people who do not qualify as transgendered.
It carries no negative connotations, just serves as a simple term to describe something that would otherwise take more words to properly state.