This word is a combination of two swedish word parts. The obvious one being fitta
, which means pussy, and the second one is an ending to some common words (hängsle, vassle, etc).
There is no exact definition for what the word means. It is more like an abstract concept that resembles something. It resembles the femaleness of a woman, the smell of pussy, the consistency of the liquids coming from the pussy, and other female anatomics related to the pussy.
Lana from Smallville has a rather sour, mild fittsle.