onlooker

n.旁观者

one-armed bandit, one-horse, one-liner, one-man band, one-man show, one-night stand, one-off, one-sided, one-sidedly, one-sidedness, one-time, one-to-one, one-track mind, one-upmanship, one-way, onerous, oneself, ongoing, onion, online, only, only that, only too, ono, onomatopoeia, onomatopoeic, onrush, onset, onshore, onside, onslaught, onto, onto (also on to), ontological, ontology, onus, onward, onward(s), onyx, oodles,