Short for Roach Mobile. While smoking a blunt, when it gets to roach size, grab a plastic bottle. Burn a hole the size of your thumb for the carb hole which is covered with a finger during inhalation and then released to clear the bottle of smoke. Burn a hole for the blunt, making sure the size of the hole is just right so the blunt wont drop through. Put your thumb on the carb hole and inhale till the bottle is full of smoke. Release your thumb and inhale.