onlooker

noun

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.”

   “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.”

   “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.”

   “Please allow me to adjust my pants So that I may dance the good time dance And put the onlookers and innocent bystanders into a trance”