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1.
All-time best street bike ever built. Introduced by Harley Davidson in 1957 to combat the invading British Triumphs, Nortons and BSAs on the track and on the street. The best selling middleweight motorcycle in history.

Unique among Harleys, the Sportster engine and transmission are in one case, whereas the so-called Big Twins have a seperate transmission case. Pre 1986 Sportsters featured iron heads and are called (DUH!) Ironheads. '86 to present are the next generation Evolution, or Evo, Sportster and feature alloy heads and a 5-speed transmission. The most recent models feature rubber-mounted engines.

Sportster-based motorcycles have dominated flat-track racing since the late 1960s. Many early choppers and customs were built from Sportsters, as well as land speed record bikes.

Calling a Sportster a "girl's bike" or "Shortster" may result in a visit to a dentist.
Lots of Yuppie Softail wankers ignore the fact an 883 Sportster makes almost as many horses as their Evo Big Twin, but the Sporty is two hundred pounds lighter. No contest, Sportsters kick ass!
by Dr. Badwrench July 10, 2006
 
2.
One who plays sports or can easily pick up a new sport.
John is such a sportster; he plays soccer, baseball, and lacrosse.

Mike is such a sportster, he started playing football last year and he's already the starting running back.
by tveit March 27, 2012