An overly cocky asshat. MK is an abbreviation, which is most commonly used. Originated from an internet user's name who was such an overly cocky asshat that his name started to become an insult on the site he went to.
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".