The term mob has three main meanings.
2. By extension from the above definition, the term 'mob' became used to describe criminal gangs, and the apparatus of organized crime.
3. In Australia, the word has a much broader meaning. While still retaining its general reference to a group, the word has lost its negative connotation and has in many instances replaced flock (sheep, birds), herd (cattle) and even humans... (I've got this mob of kids arriving for Johno's birthday party tomorra.) The use of the word "mob" for a group of kangaroos is now official parlance - the term was taken into the vernacular of the Aboriginal peoples during the 19th century and has reappeared as part of Australian English today.