Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

444. Spectator — N. spectator, beholder, observer, looker-on,

onlooker, witness, eyewitness, bystander, passer by; sightseer; rubberneck, rubbernecker [U.S.]. spy; sentinel &c (warning) 668. V. witness, behold &c (see) 441; look on &c (be present) 186; gawk, rubber [Slang], rubberneck [U.S.].