Bystander

Noun

 * 1) a person who, although present at some event, does not take part in it; an observer or spectator

Thesaurus
TV-viewer, abutter, adjoiner, attestant, attestator, attester, beholder, bird-watcher, borderer, cojuror, compurgator, deponent, drugstore cowboy, earwitness, eyewitness, gaper, gazer, gazer-on, girl-watcher, goggler, immediate neighbor, informant, informer, kibitzer, looker, looker-on, neighbor, neighborer, observer, ogler, onlooker, passerby, perceiver, percipient, seer, sidewalk superintendent, spectator, spectatress, spectatrix, swearer, tangent, televiewer, television-viewer, testifier, video-gazer, viewer, voucher, watcher, witness