tenebrous

ten•e•brous (TEN-uh-bruhs)  adj

Definition:
1. shut off from the light : dark, murky
2. hard to understand : obscure
3. causing gloom

tenebrosity, tenebrousness noun

Origin:
1375–1425; from O.Fr. tenebreus (11c.), from L. tenebrosus, from tenebrae "darkness"

Related:
Synonyms: dark, ominous, caliginous, murky, obscure, shadowy, shady, unclear, unilluminated, unintelligible, unlit, tenebrious
Related Words: temerity

Sentence Examples:
• The first dreamers, who were called philosophers imagined that matter and light were co-eternal; they supposed that was all one unformed and tenebrous mass; and from the former they established the principle of evil and of all imperfection, while they regarded the latter as sovereign perfection.  -The Satyricon, Petronius Arbiter
• A few days later he saw at his club a gentleman of his acquaintance, named Austin, who was famous for his intimate knowledge of London life, both in its tenebrous and luminous phases.  -The Great God Pan, Arthur Machen
• But her imagination was roving in the dim oil-lit streets of the tenebrous city, striving for the clairvoyance of love. -Dreamers of the Ghetto, I. Zangwill

The Storyline
She scanned his face for signs of some reason for the sudden and unexpected appearance. But his motives and countenance remained tenebrous.

Sources: Merriam-Webster, Online Etymology

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