Turbidity

"The amount of solid particles that are suspended in water and that cause light rays shining through the water to scatter. Thus, turbidity makes the water cloudy or even opaque in extreme cases. Turbidity is measured in nephelometric turbidity units (NTU)." (U.S. Geological Survey, 2019)

Sources

U.S. Geological Survey (USGS). "Water Science Glossary Terms". USGS Water Science School. (2019). Link: https://water.usgs.gov/edu/dictionary.html#W