Opaque.
1. not transparent or translucent; impenetrable to light; not allowing light to pass through.
2. not transmitting radiation, sound, heat, etc.
3. not shining or bright; dark; dull.
4. hard to understand; not clear or lucid; obscure: The problem remains opaque despite explanations.
5. dull, stupid, or unintelligent.
In other words, the author needs a dictionary.