The word is used to describe a person who has a large ego despite their obvious mediocrity.
Commonly used in some parts of Australia, the word's namesake is a lower division Australian soccer player named Frezegi who constantly touted his ability in not only the sport, but also the fields of music, billiards, dancing and acting. Despite his infamous boasting, he was usually outdone by his clearly superior, often Italian, opponents.
He lost the ball again and is still bragging, the frezness is blinding.
See: Jens Lehmann