I can't tell you what it *does* mean, but I can report what others *think* it means.
In the '70's USA, there was a show called 'The Muppet Show', which was a 1/2 hour skit show, shown on prime time, what featured the muppets in skits, and various guests like Alice Cooper and Elton John. It was insanely popular. One of the reoccuring characters was 'The Swedish Chef', who mumbled an incomprehensible sort of Swedlish while trying to cook things like meatballs and the like. Hilarity always ensued as his cooking would go massively awry, like the time he got held up by a horde of bandit lobsters. But, I digress. He'd have a little song in the beginning, and he'd end it by shouting "Bork! Bork! Bork!".
So, fast forward to now. Fellow Americans will ask me about my shirt, or what I'm listening to, and the like, and if it's Borknagar, I'd tell them that. And if they're part of the 99.9% of the population that's not familiar with the Norwegian Black Metal scene, they'd look really confused. Then, they'd pull a face, and usually ask me to repeat the name. Then, their face would light up, as if they'd just discovered something really awe inspiring, and they'd start giggling. Then, they'd start doing imitations of The Swedish Chef, singing "Bork! Bork! Bork!" and laughing. It doesn't help that, when they finally calm down enough to ask about the band, I tell them that their current lead singer is actually Swedish.
So consequently, the Swedish Chef has a new occupation. On behalf of my country, I'd like to apologize. (And also for that George Bush thing. We're trying to fix that. Our bad.
)