It stands for "Child Rebel Soldier", the rap super group consisting of Lupe Fiasco, Kanye West and Pharrell Williams. Although still busy working on their personal albums, they still have one song called "Us Placers" which can be found in West's "Can't Tell Me Nothing" mixtape.
Download it. Real hip hop is making its comeback.
"hey have you listened to us placers by crs?"
"yeah man that shit is DOPE"