Green’s Dictionary of Slang

1. a member of a youth cult whose members wear leather, ride powerful motorcycles and fight their ritual rivals, the ‘Mods’; latterly the hardcore rockers developed into a UK version of the US Hell’s Angels (however, note cit. 1967).

1964		Macguire in New Society 28 May n.p.: The recent gang-style rioting between Mods and Rockers.
1964		N.Y. Times 7 June 72/1: Long-haired leather-jacketed, aggressively masculine, motor-cycling Rockers.
1966		T. Keyes All Night Stand 54: So the rockers can’t throw them overboard on the day trips to Le Touquet.
1967		Oz 3 6/3: The Hells Angels, California’s guerilla force of rockers.
1971		J. Mandelkau Buttons 25: He was a Mod and I was a Rocker. Life was that simple.
1977		Daily Mirror 19 Aug. 2: Rockers in studded leather gear.
1999		Indep. on Sun. Real Life 1 Aug. 1: They weren’t called bikers then. They weren’t even called Rockers in the early days. They were ‘the Lads’.
2000		Indep. Rev. 11 Feb. 14: And when all the Fifties rockers / Have been buried in their graves.
2010		K. Richards Life 74: The opposite of that fashionista stuff was your rockers and your motorbike racers.

2. a fan of rock music; also as adj.

1977		C. McFadden Serial 33: Grade-school rockers plugged into all the earphones.
1991		D. Gaines Teenage Wasteland 85: Adults are never going to trust these rocker kids to do their own thing.
1999		Guardian 23 Sept. 20: Bowie is not and has never been a rocker.