I have had ZuDefinition speakers for years - initially Def1.5, them Def2, and finally Def4. Each version has been a significant step forward. I take advantage of the high sensitivity to drive them with an 300b SET. Every company in every industry has its own marketing terminology and hype. Audio is no exception. I care less about the buzz words that Zu uses than about the sound. Some people love the Zu sound; some do not. I fall into the first group as does everyone who hears my rig. The new Druid VI are also really good.