onlooker
noun
[ ˈɒnlʊkə ]
• a non-participating observer; a spectator.
• "a crowd of fascinated onlookers"
Similar:
eyewitness,
witness,
observer,
looker-on,
fly on the wall,
spectator,
watcher,
viewer,
sightseer,
bystander,
non-participant,
rubberneck,
beholder,
