From Longman Dictionary of Contemporary Englishonlookeron‧look‧er /ˈɒnˌlʊkə $ ˈɑːn-, ˈɒːn-/ noun [countable] WATCHsomeone who watches something happening without being involved in it A crowd of onlookers had gathered at the scene of the accident. → look on at look1
Examples from the Corpus
onlooker• The concept of county supervisor as onlooker is presented throughout the proposed charter.• About 40 curious onlookers stood by as firefighters cut the windshield with an ax.• The child glanced fearfully around the small circle of onlookers.• A crowd of onlookers gathered at the scene of the accident.• The last few runners appeared, to an accompanying cheer from the crowd of onlookers.• The crowd of onlookers had grown.• And there was a good turn out of onlookers on the river bank.• With his free hand, he beckoned the startled onlookers to come closer.• With a terrible flash that all but blinded the onlookers the island vanished, around it the storm of magical energy.• This was achieved by turning half away with a repressed sigh so that the onlooker observed the profile which photographed very pleasingly.• The soldiers so blocked spectators' view that the onlookers cheered, thinking the president was in the carriage. 