A phrase used as a substitute for "totally awesome".
Often used by people who are into video game style music.
It is widely believed that Mike Cook of Spheres of chaos and the gamewave podcast coined this phrase.
Although this phrase can and is often used to describe the awesomeness of atari music, it is not exclusive and can be used to describe anything from music to your best friends sisters new haircut.
"Have you heard the new GOTO80 EP? It's Proper Atari."
"Dude, your mom looks Proper Atari in that sweater, she's really slutting it up since your dad left, huh?"