When you are with your "bros" in a public place, and you see an attractive female, instead of saying, "check out that hot chick," one would say "yo dude, bro call to the right." It can also be used as a question. "Is that chick a bro call man?"
The bro call ensures that guys can openly discuss a female's appearance without her knowing.
Dude, is that chick a bro call?
Hey man, check out that bro call, straight ahead.