Its Boogie's buzz word for their EL84 power amp section. It's very tight and responsive to pick attack, very snappy and expressive. It can also sound a lot louder than its rated wattage because of the great transient response on the attack. It's not as compressed sounding as their 6L6 based power sections (which may or may not be a good thing depending on your style). At least that is my experience. Your milage may vary.
