To me it's a long-travel trailbike (5-6" both ends) that has an effecient enough rear suspension design or shock to allow it to be pedalled through most uphill sections of any trail; beefy enough to withstand aggressive riding down hill; and with little or no chain-growth issues so that you can confidently run three rings and a front derailleur without worrying about dropping the chain due to suspension movement when the going gets really rough and fast.