opacous

adjective2

1. •
   (no longer used) Not allowing the passage of light; opaque.

   • [I]f you take ammel that is almost opacous, and grind it very well on a Porphyry, or Serpentine, the small particles will by reason of their flaws, appear perfectly opacous […] — 1665
2. •
   (literary, no longer used) Not shining or illuminated; dark.

   • The firm opacous Globe / Of this round World, whose first convex divides / The luminous inferior Orbs. — 1667