Yard Bull 

A railroad police officer. Often just referred to as a "Bull" by tramps, hobos, and graffiti artists. Their job is to secure rail yards and prevent theft from or damage to railroad property.

When riding the rails, you have to look out for the local Yard Bull.

Yard Bull by Jacaranda January 6, 2008

barn yard bully 

A person who rapes every animal on a farm.

Your brother is a barn yard bully.

barn yard bully by Eric Buzz. April 28, 2007

Yardbull 

A police officer who patrols train yards looking for train-hoppers, oogles, crusties, etc.

Man, did you see that fat yardbull chase us through the train yard?!

Yardbull by John Jacob Gingleheimerschmidt February 22, 2011