Analogous to "All Bark, No Bite". A person who is a loud, obnoxious, overly aggressive jackass, but without anything to back up the behavior. It's is like having a thick two-inch dick with a huge head, impressive to the owner but basically useless.
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".