Green’s Dictionary of Slang

easy rider n.²

[from the film of that name (1969)]

any ‘outlaw’ motorcyclist.

1975		G. Underwood ‘Razorback Sl.’ in AS L:1/2 58: easy rider n Counterculture motorcyclist.
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 40: EASY RIDER — A biker.