It's a synonym for fucking badass metal.
These guys may not be original in the sense of being a ground-breaking group, but in a time where truly talented heavy metal bands are hard to come by, 3IOB fills the gap perfectly. They are somewhere between thrash, speed, and power metal. In other words, they are a heavier, thrashier version of Iron Maiden and Judas Priest. The vocals are great, although many people would consider them "weird" compared to the douchebaggery-filled voice of Nickelback's singer. Some fans of 3 Inches of Blood, myself included, think that the band could stand to improve by removing the metalcore vocals of Jamie Hooper, but if that's the only problem they have, then who the fuck cares, they kick more ass than is humanly necessary and then some. And then some more. And more. And more.
2 weeks ago, I heard 3 Inches of Blood for the first time. They kicked my ass. Hard.
too long; didn't read: 3 INCHES OF BLOOD=FREAKIN AWESOME METAL.