opacous

O1P3A1C3O1U1S1

adjective

Not shining or illuminated; dark.

OriginLatin opācus →
First used 17th–20th c.Scrabble 11
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Meanings

adjectiveopacous (not comparable)
  1. not comparableobsoletepoeticNot shining or illuminated; dark.First known use 17th–20th c.

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

    1667, John Milton, “(please specify the page number)”, in Paradise Lost. […], London: […] [Samuel Simmons], and are to be sold by Peter Parker […]; [a]nd by Robert Boulter […]; [a]nd Matthias Walker, […], →OCLC; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873, →OCLC
  2. not comparableobsoleteNot allowing the passage of light; opaque.First known use 17th–19th c.

    The upper wings are opacous; at their hinder ends, where they lap over, transparent, like the wing of a fly.

    1681, Nehemiah Grew, Musæum Regalis Societatis. Or A Catalogue & Description of the Natural and Artificial Rarities Belonging to the Royal Society and Preserved at Gresham Colledge. […], London: […] W. Rawlins, for the author, →OCLC
    2 more examples

    And vve particularly remember, that, being at ſome diſtance from London one Night, that the People, upon a very vvell-come Occaſion, teſtified their Joy by numerous Bon-fires; though, by reaſon of the Interpoſition of the Houſes, vve could not ſee the Fires themſelves, yet vve could plainly ſee the Air all enlighten'd over and near the City; vvhich argu'd, that the lucid Beams ſhot upvvards from the Fires, met in the Air with the Corpuſcles opacous enough to reflect them to our Eyes.

    1659 December 30 (date written), Robert Boyle, “[Experiment 37]”, in New Experiments Physico-Mechanicall, Touching the Spring of the Air, and Its Effects […], Oxford, Oxfordshire: […] H[enry] Hall, printer to the University, for Tho[mas] Robinson, published 1660, →OCLC, page 309

    [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, R[obert] Hooke, chapter X, in Micrographia: Or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses. […], London: […] Jo[hn] Martyn, and Ja[mes] Allestry, printers to the Royal Society, […], →OCLC

Synonyms & antonyms

Also see
denseopaquethick

Origin

  1. Latinopācus“shaded, shady, dark”
  2. Englishopacous

From Latin opācus (“shaded, shady, dark”) + -ous.

More words from Latin

Full word history & related roots →
Cite this entry
APA

opacous. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/opacous

MLA

“opacous.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/opacous. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “opacous,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/opacous.

Source: opacous on Wiktionary, CC BY-SA 4.0.