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• opalescence
• over
• Oman
• outsmart
• ole
• omniscient
• outdoor
• outline
• ordain
• origin
• orientation
• odor
• ooze
• obligation
• orchestrate
• ostentation
• overlay
• onerous
• outskirts
• opulent
• outward
• ogre
• outre
• old-fashioned
• oath
• obelisk
• occupied
• overlook
• once
• obscure
• organized
• ornate
• overwrought
• overpass
• obloquy
• oriental
• often
• oversight
• old
• obedience
• obliging
• opportune
• opera
• octave
• ordinary
• onus
• observer
• opaque
• ornamentation
• orchestra
• orbit
• ordinance
• ocean
• overflow
• obituary
• officiate
• ostensible
• oration
• opinion
• opposition
• orb
• onwards
• overdose
• occlusion
• originality
• outperform
• operant
• outfit
• outlandish
• omelette
• operate
• outcome
• occupation
• outlet
• organization
• overhaul
• Orleans
• original
• owl
• outer
• overview
• occupancy
• occupant
• obtuse
• overdue
• oak
• opus
• obvious
• open-minded
• overage
• overcome
• overt
• offset
• oven
• occasional
• Oedipus
• orator
• on
• orphan
• oar
• onset
• oblivion
• onion
• operator
• opacity
• occasion
• outcast
• outlier
• outspoken
• outset
• observe
• order
• operetta
• outlook
• overly
• optical
• orange
• offertory
• occupational
• object

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因篇幅关系，字母O开头的单词只列出前 120 个；字母O开头的英语单词由君君词典提供查询