The Mafia can establish a 'Government' with a set of well-defined laws and coerce people into abiding by them as well.
As can trade unions by overthrowing the Government and 'seizing the means of production'.
As can a group of businessmen looking to maximise profits by establishing monopolies through licenses and permits.
All of the above has coercion and aggression involved, and would amount to Socialism. I generalised my definition to include them.