"Hobnocker" is a completely made up word from the nickelodeon show iCarly.
All of the previous definitions were written to Urban Dictionary AFTER the episode of iCarly with the meaningless word aired early 2009, all of the previous comments being a little bit later on.
The only description (from the episode of iCarly) is "gross... and illegal"
A hobnocker is someone that does something illegal and gross (not to be confused with "hobnobber," which is a cool and awesome geek).
A hobnocker is someone that is addicted to illegal drugs.
A hobnocker is an alcoholic.
A hobnocker is a derogatory term describing a lowlife and pervert.
A hobnocker is a person who goes around slapping people with their genitalia.