An aimless wanderer, someone without a permanent home, is a drifter. Your distant cousin who parks his camper in your driveway for a few weeks and then moves on? You can call him a drifter.
The original meaning of drifter was a miner whose job was excavating horizontal tunnels, which were known as drifts. Starting around 1880, it was also used for a type of fishing boat that used drift nets. For most of the 20th century, however, the most common use of drifter was to describe a vagrant, homeless person, or someone whose lifestyle involved drifting from place to place.