mooner

noun

1. One who abstractedly wanders or gazes about.

   “A "mooner," fond of staring into shop windows, or watching the labourers pulling up the pavement to inspect the gas-pipes, or listening stolidly to the dull "pech" of the paviour's rammer on the flags.”

2. Someone who moons (drops their pants and shows their bare buttocks in public).

   “Though not an exhibitionist mooner like Rousseau, Jacques offers us his belaboured rump as an image of a brutalised, not loveless but misloved, childhood .”

3. A lunatic.