MAMIL
n. A middle-aged man who is a devotee of cycling or some other sport that requires or encourages the wearing of Lycra.
Etymology
Examples
2014
These "middle-aged men in lycra" or MAMILs, as the tribe has unflatteringly been dubbed, will be out in force this weekend as the Tour de France begins in the northern English country of Yorkshire, many of them wearing day-glo outfits and tight shorts.
—“Britain's 'Mamils' switch Ferraris for expensive bikes,” Agence France-Presse, July 04, 2014
2014
In 1986, when I first turned professional, you were viewed as some sort of freak if you rode a bike…but now there are Mamils and Mawils (Middle Aged Women In Lycra) everywhere.
—Paul Kimmage, “Pedalling your way to paradise in Majorca,” Sunday Independent, June 15, 2014
2007 (earliest)
This disappointed many expensively kitted-out MAMILs (middle-aged men in lycra) who take their ocean swimming seriously.
—Clay Lucas, “Swimmers rough it as they test open water course,” The Age (Melbourne, Australia), March 13, 2007
Notes
How about an equal opportunity photo of the middle aged women in Lycra (MAWIL)? Those ladies are in some great shape!
—windyscotty, “Re: Rise of the MAMILs: Middle Aged Men in Lycra” (reply), Eastern Sierra Forum, August 19, 2010