the term refers to one that serves as a drinking companion, specifically to a bar.
a bartner can be a friend, relative, classmate, coworker, etc.
an ideal bartner would be one who enjoys a similar drinking environment, holds a similar (or superior) alcohol tolerance, has similar taste in the opposite sex, is skilled at acquiring rides, etc.
After their microbiology exam, Pete and Tom bumped into each other at the local bar. From that day on, they were bartners.
Although Lisa and Tina had little to talk about at work, they were the best of bartners once Friday rolled around.
A cyren is any girl who appears very attractive on her online social networking page (e.g. Facebook, Myspace, etc.), but in reality is mediocre, at best. The word is a hybrid form of the words "cyber" and "siren."
My friend Brandon thought he had discovered an online babe. Turns out, she was a total cyren.
Friend 1: Dude, this babe just added me on facebook. I think she wants a piece.
Friend 2: Oh no, stay away from that chick. She's friends with my ex, and is the omega-cyren! TRUST ME.