from answers.com:
buy.In sports, the term dynasty may refer to a team that enjoys a period of dominance over the sport, generally gauged via championship titles.
Lance totally falls in line with that...I mean cycling is a hard sport, especially in the tour de france. To bike across the alps, pyrenees, and to dominate it 7 times in a row? I would totally consider that a dynasty. I know theres going to be some people in here that are going to say "oh well i mean the pats are a dynasty, the 60's celtics were a dynasty, blah blah blah" well they are, but dynastys don't happen in just team sports. a person can be a dynasty too.