obscuration

The state of being obscured.

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!

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.

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.