-It's a thick black swirl (I think one of the girls has a bit of green in hers)
-It only wraps around itself like twice
-It's very basic, it is just a 2-dimensional swirl that is shaded in completely. It doesn't have any shadow or anything else with it
I can't find any images of it, but if you know what I'm talking about please include a link to a picture!
Also, it's not a trendy looking tattoo...it's extremely basic, so that is why I am guessing there is a real meaning!