At some point in the 90's, the word "dude" became a ubiquitous signifier of masculine cool. And then it was quickly adopted by cool women. Nowadays, only forty-five year old branding consultants in San Diego with ponytails still refer to each other as dude. The word dude has not been uttered on a college campus in at least five years. It has been replaced by something new, and far more insidious: "bro."

Step onto any state college campus, and you'll be greeted with a cacophony of "bros." What does it all mean? The word is robust and has numerous meanings. Among the most well-known:

THE CONDESCENDING BRO
This can be effectively used as a stand-alone ("bro!") or at the end of a sentence. It is used to chastise other males for behavior that the group considers collectively uncool, such as clogging the frat house toilet, hitting on another bro's girlfriend, and so forth.

THE CONGRATULATORY BRO
Most often heard as a stand-alone, it is a way of congratulating a fellow bro on a job well done. For example, if your roommate shows you the Facebook profile of the girl he hooked up with last night, and she's attractive, "Bro!" is an acceptable form of flattery.

BRO AS MORAL GUIDEPOST
First popularized by a series of t-shirts sold online, these phrases impart crucial societal values that vary depending on the campus and climate. "Bros before hos," for example, is used to express the concept that bros should not neglect or betray their male ties in pursuit of a casual hook-up. "Bros before prose," on the other hand, promotes a certain anti-intellectual sentiment: finish that f'ing kegger off before you get back to reading Arendt.

THE INTERROGATIVE BRO
When you suspect foul play, such as a missing stick of deodorant or your roommate Facebook poking your girlfriend several times in one week, you can bring up the subject with a simple (and devastating) "Bro?" Also can be used to wake someone up in the morning, or to check on another male's emotional well-being without appearing too
sensitive.

David Seaman is the author of DIRTY LITTLE SECRETS OF BUZZ, in stores next year. He has appeared as a guest on CNN Headline News, CN8, Sirius Satellite Radio and elsewhere.