Opaque

Part of speech: adjective

Pronunciation: /əʊˈpeɪk/

Definitions

1. Not allowing light to pass through; impossible to see through clearly
2. Not permitting the passage of light
3. difficult to understand or perceive

Etymology: Latin "opacus" meant "shaded" or "shady," and it was used of places and things that were covered over or kept from the sun. Its own origin is unknown, so the trail stops there. English picked it up in its Middle English form "opake," and the word was later reinforced by the French "opaque," which had the same sense of blocking light. The most striking thing about the word is its doublet, "ubac," a term from the study of mountain slopes. "Ubac" describes the shaded side of a valley or mountain, the face that faces away from the sun. Both words descend from the same Latin root, one having come through French into English and the other taking a different path, so a term for a dim hillside and a word for a substance that cannot be seen through share a common ancestor.

Synonyms: cloudy, hazy, murky, nontransparent

Antonyms: transparent, clear, lucid, see-through