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• oppression
• overflow
• ovation
• overload
• operose
• offence
• opposite
• offense
• ovum
• organism
• occupational
• odoriferous
• obsolete
• ornamentation
• open-minded
• officious
• originate
• outlawry
• obituary
• orderly
• overture
• outpouring
• oration
• outlaw
• outsider
• occur
• offensive
• OS
• or
• oatmeal
• oil
• observatory
• openly
• outskirts
• outstanding
• obscene
• occultation
• occult
• oaf
• otherness
• on
• outlet
• outdoor
• o
• overview
• om
• oriental
• onus
• opposition
• orphanage
• old
• outlook
• omphalos
• outpost
• onward
• outside
• out
• oddness
• otherwise
• off-chance
• orbit
• oneness
• outnumber
• outage
• optimistic
• offering
• outlander
• outrage
• outdoors
• official
• outgrowth
• OPEC
• obedience
• overdo
• omer
• onslaught
• origin
• overstate
• opening
• organisation
• overrun
• offer
• omelette
• October
• occasionally
• overwrought
• ornithology
• observance
• orotund
• outfit
• orbicular
• original
• obese
• orchestra
• organizer
• outline
• occupied
• overrate
• obloquy
• overhead
• officer
• oligarchy
• operetta
• orientation
• ordain
• omnipotence
• occurrence
• oneself
• objection
• over
• opener
• organized
• outing
• off
• order
• oxide
• odometer
• outreach
• obey
• outperform

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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