- The definition of a bystander is a person who stands near but doesn't take part in an event.
Someone who happens to walk into a store while it's being robbed is an example of a bystander.
bystander definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a person who stands near but does not participate; mere onlooker
bystander definition by American Heritage Dictionary
A person who is present at an event without participating in it.