A Harley Davidson Sportster motorcycle customized to resemble a Fat Boy model, usually with a wider front end, larger gas tank, and lower fenders. People create fatsters both because it is much less expensive than buying a Fat Boy and also because the Sportster models have much faster engines than the slower Fat Boys. Sportster models are often looked down upon as being "girl bikes" because they are often the less expensive models which men will buy for their wives, and this may play a role in the desire to change their appearance.
I couldn't believe that Bill bought a Sportster until he turned it into a Fatster.
by Nefariouslacker January 15, 2009