A person who is present at an event without participating in it.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "bystander" in a sentence
"I will use the term participation unit to refer both to encounters and to unengaged participants; the term bystander will be used to refer to any individual present who is not a ratified member of the particular encounter in question, whether or not he is currently a member of some other encounter."
""He must have played rugby for years to have developed reflexes like that," a bystander is quoted by Reuters as saying."
"The first version tells us something that should be obvious: this bystander is surprised."