Definition of Dead

How do we really define what is dead? Does a beating heart make you alive? Because by definition that should be true. Yet, though my heart beats in my chest I find myself strangely obessed With wanting to feel Like I'm really alive With wanting to prove to myself that I've Not really been dead, Just in a long sleep. And one day I'll wake out of this bleak World that's suffocating me inside and out But the longer I live The more that I doubt I'll ever escape The prison I've built inside my head So I'll ask you again, What defines being dead?