To push one's fist right into another's asshole. This is also called an JAM UP. Normally used in times of extreme agressiveness. Males in particular detest this as it enlarges the rectal passage by up to six times.
explainza.com | 🔎
Our projects: Financial Independence: Your personal finances in the cloud | CatamaranAdvisor: Catamaran database, catamaran specifications, photos of catamaran interiors and exteriors