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Webster 1913 Edition

Noun.

One who abstractedly wanders or gazes about, as if moonstruck.

[R.]

Dickens.

mooner ‎(plural mooners)

One who abstractedly wanders or gazes about.
- 1853, Charles Dickens, Household Words (volume 6, page 387)
  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.
Someone who moons (drops their pants and shows their bare buttocks in public).
- 2009 October 13, "Train drags mooner half-naked along tracks", Syney Morning Herald.
A lunatic.