1. The unbridled mane of one's buttocks. (see manscaping
2. The area which a bum
claims to be his own to collect his income. Bum turf may be, and usually is fought for. Many a bum have lost their turf due to drunkeness, or inability to stand their ground.
"Man my ass itches"
"I've got stubble because I just shaved my bum turf"
"There's broken glass, vomit and shit everywhere"
"Yeah, I saw a couple of guys fighting over their bum turf"
"Why do you need to share my bum turf?"
"Because I went back to mine, and found a couple of fags in my box, and I knew what they were doing because the velcro sound. It must've been the rubbing of bum turf on freshly manscaped crotch"