A chopper is a radically customized motorcycle, archetypal examples
of which are the customized Harley-Davidsons seen in the 1969 film
Easy Rider.
Many of today's custom motorcycles are sometimes mistakenly called
choppers, but a truly custom-built motorcycle has additional -usually
chrome - accessories and billet parts added on to the bike for aesthetic
value, while originally such modifications were purely functional in nature.