From BZPB Spin-Offs
The meat grinder is a machine intended to grind meat. However, on BZPB, it is more often used to grind people.
A use of the meat grinder is typically preceded by Shroom saying "He knows too much. Meat-grind 'im.". Alternatively, he could just kick you into a meat grinder without saying anything.
As one of Shroom's memes, there is a tax on using it. If you complain about it, Shroom will kick you into a meat grinder.