A biker is an informal descriptor of someone who is a motorcycle enthusiast. In addition to riding and the maintenance of motorcycles, common stereotypes would describe a biker as a rugged, tough-looking individual (usually male) with an unkempt appearance, often sporting a big mustache and/or beard (again, usually male, but this is not always a guarantee). American bikers pride themselves on their ride, which is usually some model of Harley-Davidson motorcycle.
From Dusk Till Dawn: In Mexico, the Titty Twister was a bar that catered to bikers and truckers only. Although Jacob Fuller declared himself a trucker, there were many tough looking hombres who rode their bikes to this establishment. Unfortunately they were all lunched by vampires. Not psychos. Vampires.
The Walking Dead: A biker gang known as the Saviors operated in Virginia near Alexandria under the leadership of Negan. One of Negan's scouts and his gang encountered Dary Dixon, Abraham Ford, and Sasha Williams on a highway. They took their weapons and were prepared to kill them until Daryl produced a rocket launcher and blew the entire gang to smithereens. (Walking Dead: No Way Out)