What is the definition of Settled Fluid?

A 'ettled fluid' is like the still pond after a storm - it might look calm on the surface but holds secrets beneath. Imagine this: "After the nuclear meltdown, the 'ettled fluid' in the cooling reactor room was just a tiny, radioactive puddle that seemed to be whispering 'I'm fine, just a little radon in my head' to anyone who dared listen."