* Relating to or characteristic of a sect or sects. A sect is a group of people with somewhat different religious beliefs or practices than the larger group they came from. For example, you might say "the sectarian violence in Northern Ireland" referring to conflict between different religious groups.
* Narrowly confined to a particular group or party. This meaning suggests a lack of inclusivity or openness to other perspectives. For example, you might say "the sectarian nature of the debate" to describe a discussion where people are only interested in hearing their own side of the issue.
If you have a specific context in mind, please provide it so I can give you a more precise answer.