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Webster 1913 Edition

Noun.

The falling of dew; the time when dew begins to fall.

See also: dew-fall

dewfall ‎(plural dewfalls)

The forming of dew.
The time when dew begins to form.
- 1979, Cormac McCarthy, Suttree, Random House, p.44:
  It was dark when they rose in the morning and dark when they filed into the kitchen to get their plates and spoons and still dark when they turned out in the dewfall and grainy mist of the yard.

forming of dew

time when dew begins to form