crack cocaine - Wiktionary, the free dictionary
From Wiktionary, the free dictionary

So named due to the crackling sound of the pieces when it is smoked.
- A mixture of baking soda and cocaine in solid form that is smoked in a pipe as a narcotic.
- A mixture of salt substitute, ether, and cocaine in a semi-liquid form, which is far more potent than if made with baking soda alone.
crack cocaine on Wikipedia.Wikipedia