Progressive is one loaded word. Webster’s defines it as “moving forward or onward,” but it has a far different meaning in the rock world. Therein lies the quandary for the British rock quartet Porcupine Tree.

On its U.S. debut album, “Signify” (released Jan. 13 on ARK 21), Porcupine Tree travels trippy terrain carved by Pink Floyd and King Crimson, but singer-guitarist Steven Wilson and his band mates have more in common with Radiohead and Kula Shaker, taking the classic rock format and putting it in a modern rock context.

“My whole motivation with the project was that I felt there was a tremendous scope for someone to do something quite different with the ’70s psychedelic space rock, whatever you want to call it,” Wilson said recently, “but combining it with very modern influences and using modern technology. All those bands in the ’70s, they were making use of the up-to-date, contemporary recording, the techniques that were available, and making something unique.

“The problem with some bands who take influences from that era, they really don’t take on board the actual ideology or philosophy of the music. They just look away, recreating it for almost nostalgic reasons. I can’t see the point of doing that at all.”

Wilson, Richard Barbieri (synthesizers), Colin Edwin (bass) and Chris Maitland (drums) have been pushing the pop envelope throughout the 1990s, along the way gathering legions of mostly European fans, but they have been saddled with the label “progressive rock.” It makes Wilson cringe.

“If you use the term ‘progressive’ in England, it’s the kiss of death,” Wilson said. “It’s assuming that you sound like Genesis or something like that. They think of it as being very retro, very pompous and very naif. That’s three things that Porcupine Tree are as far removed from as you can possibly be.

“To take the true sense of the word, you move forward to try and do something different. Progressive has become a way of labeling a specific kind of music that was popular years ago, and that’s certainly not what Porcupine Tree is about. I’m not even sure I know what would be progressive rock. For me, progressive music now would be something like what DJ Shadow is doing, because that’s using the most modern technology available and taking lots of different sounds and influences and combining them together.”

Whether all that translates to progressing in the U.S. marketplace is another matter.

“I don’t understand the American market at all; I don’t understand how any band can become successful in America,” Wilson said. “It seems the whole media thing is so fragmented. In England, it’s very easy to become successful if you can crack two or three things, like radio on BBC Radio One, and if you can get good press in the NME or Q. They’re so influential on the whole scene.

“In America, you have hundreds of radio stations, hundreds of publications. It seems to crack all of them, it’s such a lottery. On the other side of it, you’ve got British bands like Bush who are big in America but are totally unknown here; I don’t think they quite understand how it happened.”