- on a daily basis
- on the part of
- on the urban scene
- on the strength of
- on the spot
- on the other side
- on the heavy side
- on the bottom
- on the battlefield
- on one's own
- on hard times
- on an equal base with
- object lesson
- of all time
- of special note
- of the day
- of the essence
- of the period
- off course
- oil refining
- parking lot
- over time
- over the horizon
- over millennia
- out of place
- other than
- originate from
- original version
- organic food
- order of magnitude
- or whatever
- operational mine
- open up
- open ended
- only that
- on various occasions
- on their way
- on the whole
- oar
- oasis
- oath
- obdurate
- obedience
- obese
- objective
- obligation
- obligatory
- obliging
- oblique
- obliterate
- oblivion
- obnoxious
- obscene
- obscure
- obsequious
- observe
- obsess
- obsolescence
- obsolete
- obstacle
- offhand
- obstinate
- obstruct
- obtrude
- obtrusive
- obtuse
- occult
- odds
- odious
- odor
- offence
- offend
- offensive
- officious
- offset
- omen
- ominous
- omit
- omnipotent
- omniscient
- onset
- ooze
- opponent
- opportune
- optical
- optimal
- optimism
- option
- opulence
- opulent
- oration
- orator
- orchestra
- ordain
- ordeal
- orient
- orientation
- original
- originality
- originate
- oscillate
- ostensible
- ostentation
- ostracize
- oust
- outbreak
- outburst
- outcome
- outfit
- outlet
- outline
- outlook
- outmoded
- output
- outrage
- outrageous
- outset
- outskirts
- outspoken
- outstanding
- ovation
- overbearing
- overdue
- overflow
- overlap
- oversight
- overstate
- overt
- overtake
- overwhelm
- overwhelming
成人英语托福单词单词大全〔O 〕课程包含131个英语单词词汇。