A term used by members of a clique to express a general disaproval of a person, group of people or activity that is not consistent with the values of their clique.
Use of the term, in this context, portrays narrow-mindedness and a lack of perspective; avoid. Remember, cool transcends cliques.
1) They don't drink? They're boring!
2) He doesn't support a football team? He's boring!
3) She isn't a complete slut? She's boring!