What is 'Dark Fluid'? Is this term official jargon/wording for 'Dark Matter'?
If so, why include the word "Fluid" if there is supposedly no viscosity in actual space. It would be like saying 'Hey, want to go swim in my 'gravel' pool?"
http://www.dailymail.co.uk/sciencetech/article-3013284/Is-dark-matter-FLUID-Mystery-particles-mapped-galaxy-clusters-results-suggest-not-particles-all.html
No, &quot;dark fluid&quot; is not a synonym for dark matter.
The Daily Mail article derives from a press release by the EPFL and an article in Science magazine, neither of which mention the word 'fluid'.
We don't know what dark matter is yet. There are several theories. One of them compares dark matter to a fluid:

Normally speaking, subatomic particles exchange momentum when they interact. Consequently, galactic collisions should also lead to interaction by dark matter particles and by studying it, we would have a better idea of what dark matter really is.
To verify whether dark matter is made up of particles, the researchers explored two possible outcomes. The first, was that particles of dark matter often interact, but don't exchange much momentum. The second was that they seldom interact, but exchange a lot of momentum.
If the first case was true, dark matter would slow down after the collision, since the greater frequency of the interactions would have drag-like effect. If the second case was proven to be true, then dark matter would likely be dispersed into space.
Surprisingly, the study discovered that the dark matter particles from two colliding galaxies, simply pass through each other, suggesting that dark matter particles do not interact with themselves, but have a more fluid-like character instead.

(emphasis mine). So they're not saying dark matter is exactly like a fluid, they're saying dark matter has some properties that are comparable to the behavior of fluids.