A bicycle with a seatpost that is not the right length for the person riding it. Tall crackhead riding bike with short seatpost / short crackhead riding bike with long seatpost so that his/her toes barely touch the ground. A good indication that the bike has either been stolen or recovered from a dumpster. Some times the bike has no seat at all.
"Look at that skinny little dude with the sunken cheeks and a beard wearing a hoodie riding the bike with the long crackhead seatpost, he's barefoot, the bike must be stolen, stupid crackheads!"