The socal defenition of a broho is a chick that sleeps with bros. (Bro being typically a person who likes to go to the desert and go offroading in a truck, dunebuggy, or on a dirtbike, quad, etc.) Brohos go for the guys that not only have beer but weed. SRH, skin, DC, Dickies, and other similar brands are common in this crowd.
Kim is such a broho! She slept with Jeremy, Ryan, Adam, Mark, Mike, Sam, Josh, Anthony, and Brian. They are all friends and have no problem with it! ugh, sooo gross (I borrowed this, it was a good example)