Means 'Cans on Display'. To be used when in the vicinity of cans, which are prominently on display, and you wish to point out to a mate that there are cans on display without notifying the owner of the cans.
*cans walk into room*
guy1: hey dude, bulls on parade son
guy2: *turns and surveys the cans* Worrdddd!!
Owner of cans: *Oblivious look*