Pitch dark means so dark that nothing at all can be seen. It was pitch dark, pitch dark outside, pitch dark by six.
The pitch is the black tar used to seal ships, which is about as dark as anything people handled before industry. True pitch dark is rare where there is any settlement, since even distant streetlights reach the clouds and come back down.
1phrasepitch darkSo dark that nothing at all can be seen.
“When the power went out, the house was pitch dark.”
pitch dark is a darkness.
Also accepted in games: pitch-dark
Practised in Light & Shadow, Shapes & Lines