Typically the vernacular of really
degenerate people.
Funnin means that someone has played a joke on you or made you look foolish.
Funnin can be as simple as ambushing unsuspecting people with a paintball gun and laughing about it or as
destructive as secretly destroying a project that someone has worked very hard on at their work.
When setting someone for funnin all of the people who were witness to it are
supposed to deny any knowledge of of the incident.