What is Shast?
1.
retarded way of saying "shit"
Oh shast!
2.
When different music from multiple sources can be heard at once.
"The cars in the parking lot are all blasting their music, and boy this is not shasting well for me."
"Wow these two songs shast surprisingly well."
See
3.
To take a dump/poop/shit
Oh man, that KFC gave me the shasts