onlooker

From on +‎ look +‎ -er, probably from the verb look on, but compare with onlook.

• IPA^(key): /ˈɒnˌlʊk.ə(ɹ)/

• Audio (Southern England)

  (file)

onlooker (plural onlookers)

1. A spectator; someone looks on or watches, without becoming involved or participating.

   I wasn’t involved in the fight; I was only an onlooker.

   • 1945 May and June, Cecil J. Allen, “British Locomotive Practice and Performance”, in Railway Magazine, page 152:

     When the right-away was given, Driver Gibson would give a sonorous blast on Cardean's deep-toned hooter, and amid a flurry of swirling steam the train would move majestically out, with nearly half the city of Carlisle—or so it would appear—as onlookers on the platform.

   • 1945 September and October, C. Hamilton Ellis, “Royal Trains—V”, in Railway Magazine, page 249:

     As a result, while the train was being shunted at Bombay, the buffers became locked, producing a situation most intriguing for the onlookers, but exasperating for the exalted passengers and the unhappy railway authorities.

• bystander

• looker-on