6 letters · 17 points in Scrabble
adjective not transmitting or reflecting light or radiant energy; impenetrable to sight
adjective not clearly understood or expressed
originFrom Middle English opake, from Latin opacus (“shaded, shady, dark”) (of unknown origin), later reinforced from Middle French opaque. Doublet of ubac.
Etymology from Wiktionary, CC BY-SA 3.0