The word sunk can have different meanings, and there are also different opinions as to more exactly what the word actually means, but those are the general lines.
First, it can refer to a feeling. This is approximately the feeling many people have at the breakfast table. Oh, come on, you know perfectly well what I mean!

Second, something can be "sunky", or sunkigt in swedish. This is a tough one, but when people say that something is "sunky", they often say it, with a certain amount of warmth in their voice, about some old and much used thing, like a pair of old shoes.

Third, you can "sunk". That is, to deliberately go into the state described in the first article. This is approximately what you do when you wake up 1100 on saturday morning with a slight hangover and spend the day in front of the TV. In a week or so, there will hopefully be a graphic representation of this one.

Graphical representaion of "sunk":
In Budapest