obscuration

obscuration (countable and uncountable, plural obscurations)

1. The state of being obscured.
   • 1843 April, Thomas Carlyle, chapter X, in Past and Present, American edition, Boston, Mass.: Charles C[offin] Little and James Brown, published 1843, →OCLC, book III (The Modern Worker):

     Money is miraculous. What miraculous facilities has it yielded, will it yield us; but also what never-imagined confusions, obscurations has it brought in; down almost to total extinction of the moral-sense in large masses of mankind!

   • 1953, Samuel Beckett, Watt, 1st American edition, New York, N.Y.: Grove Press, published 1959, →OCLC:

     At eleven the room darkened, the moon having climbed behind a tree. But the tree being small, and the moon's ascension rapid, this transit was brief, and this obscuration.

2. A unit of measurement used in particular for smoke detectors which respond to absorption of light by smoke, in percent absorption per unit length, e.g. % obs/ft, % obs/m.