To get angry at something or someone. To show disproval. A way to "stick it to the man."
(originated from a lonely island SNL music video)
I was walkin' through the city streets
And a man walks up to me and hands me the latest energy drink
"Run faster, jump higher"
Man, I'm not gonna let you poison me
I threw it on the ground
You must think I'm a joke
I ain't gonna be part of your system
Man! Pump that garbage in another man's face