opaque

Opaque, a.

Etymology: [F., fr. L. opacus. Cf. Opacous.]

1. Impervious to the rays of light; not transparent; as, an opaque substance.

2. Obscure; not clear; unintelligible. [Colloq.]

1 other Webster entry under this spelling

Opaque, n.

That which is opaque; opacity. Young.

Shades of meaning

Fernald has no entry of its own for opaque; he lists it under dark.

Where he writes about it:

Opaque objects, as smoked glass, are impervious to light. — from dark