intransitive verb
Definition: To gather or clump together into a thick, semi-solid mass, often used in reference to substances like blood cells.
Example: The blood cells began to sludge together, forming a thick mass.
noun
Definition: A thick, soft, and often muddy material that can form from waste, water, or other substances, usually found at the bottom of rivers or in sewage systems.
Example: After the heavy rain, the river was filled with sludge that made it difficult for boats to pass.