Bystander
A bystander is a person who is not participating in an activity, but is observing it.
Learn
DefinitionYour turn
Several bystanders fought back against the London attacker. A bystander is someone who is nearby, but not participating in an activity. In this case, the bystanders included a chef, two tour guides, and a plainclothes police officer. They were going about their business when the attack started; as bystanders, they had no role–at first. Then, they started fighting back.