Dark Pool Liquidity

What Does Dark Pool Liquidity Mean?
A slang term that refers to the trading volume created from institutional orders, which are unavailable to the public. The bulk of dark pool liquidity is represented by block trades facilitated away from the central exchanges.

Also referred to as the "upstairs market", or "dark liquidity", or just "dark pool."

Investopedia explains Dark Pool Liquidity
The dark pool gets its name because details of these trades are concealed from the public, clouding the transactions like murky water. Some traders that use a strategy based on liquidity feel that dark pool liquidity should be publicized.