type of motorcycle, by 1968, short for Harley-Davidson motorcycle manufacturer founded in Milwaukee, Wisconsin, U.S., 1905 by engine designer William S. Harley (1880-1943) and Arthur Davidson. The surname Harley is attested from mid-12c., literally "dweller at the hares' wood." Harley Street in London from the 1830s was associated with eminent physicians and used metonymically for "medical specialists collectively."