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Webster 1828 Edition

Noun.

unhelth'iness.

Want of health; habitual weakness or indisposition; applied to persons.

Unsoundness; want of vigor; as the unhealthiness of trees or other plants.

Unfavorableness to health; as the unhealthiness of a climate.

unhealthiness ‎(usually uncountable, plural unhealthinesses)

The state of being unhealthy.
- 1847, Charlotte Brontë, Jane Eyre, Chapter 27,
  […] I possess an old house, Ferndean Manor, even more retired and hidden than this, where I could have lodged her safely enough, had not a scruple about the unhealthiness of the situation, in the heart of a wood, made my conscience recoil from the arrangement.
- 1988, Edmund White, The Beautiful Room is Empty, New York: Vintage International, 1994, Chapter Five,
  He looked elegant and vulnerable, his eyes edging away from contact and set into a face of exquisite unhealthiness.