A person who turns up their music so loud you can hear the bass outside of the area it is being played, especially in your own apartment/house/car.
"Man, I got no sleep last night."
"Why?"
"The basstard who lives above me was at it all night with that obnoxious technomusic."
"The basstard's still alive?"
"Yeah."
"Then whose coffee did I poison...?"
A Basstard is a douchebag who insists on turning the bass up very high when listening to music. The bass ends up drowning out pretty much everything else in the song and the music basically turns into mud.
What song is that idiot listening to? I can't tell because the bass is too high. what a basstard!
That basstard doesn't even know what he's listening to. It's all just an auditory mass of sludge. He spent a lot of money on his retardedcar stereo system too. Just so that he can listen to mud and vibrate his car to pieces.