The act of taking a foreign object, placing it at the rim of your asshole and having a male take his shaft and ram it up the rectum.
"Hey Craig", Jessica Said. "Will you musket ball this battery up my lubed asshole"?
A massive ball of resin pulled from a marijuana pipe, rolled into a ball and smoked.
Dude, Charlie hadn't cleaned his bowl in like 6 months, dude pulled like 3 musket balls out.