What is the meaning of the word "dark"?

Definitions:

An unenlightened state; ignorant. NOUN
- I was in the dark concerning their intentions.
Gloomily pessimistic. ADJECTIVE
- A dark vision of the future.
Hidden from knowledge; mysterious. ADJECTIVE
- A dark secret.
Of a color or object: not reflecting much light; approaching black in shade. ADJECTIVE
- dark green
Of a period of time or situation, characterized by tragedy, unhappiness, or unpleasantness. ADJECTIVE
- The dark days of the war.
Of someone's skin, hair, or eyes, brown or black in color. ADJECTIVE
- She had dark curly hair.
Suggestive of or arising from evil characteristics or forces; sinister. ADJECTIVE
- So many dark deed had been committed.
With little or no light. ADJECTIVE
- It's too dark to see much.