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Webster 1913 Edition

Adj.

Having no depth; shallow.

Of measureless depth; unfathomable.

In clouds of

depthless

night.

Francis.

depthless ‎(not comparable)

Having no depth, or having a depth that is impossible to determine
- 2007 October 19, Holland Cotter, “King-Size Stories, Woven for the Ages”, in New York Times:
  The result is not an image of the natural world in a tapestry but a depiction of nature as a tapestry: a splendid, impenetrable, depthless screen of shivering pixels.