What is the definition of Undefined Fluid?

An 'undefined fluid' is like the ultimate cosmic vacuum cleaner – a substance that's so mysteriously indeterminate it could potentially be anything. It's the existential equivalent of a blank canvas that never gets painted, just a void waiting to be filled with whatever you imagine is possible.

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Here's an edgy example sentence: "In the face of cosmic uncertainty, we opted for undefined fluid, because nothing says 'cience' like blinking in the dark with no explanation."