- Operate under Verb
- Operationalise Verb
- Operationalize Verb
- Ophthalmoscope Subst. Verb
- Opiate Adj. Subst. Verb
- Opine Verb
- Opportune Adj. Verb
- Oppose Verb Part. Präs. Part. Perf. Subst.
- Oppress Verb
- Oppugn Verb Part. Perf. Part. Präs.
- Opsonize Verb
- Opt Verb
- Opt in Verb
- Opt out Verb
- Optate Verb
- Optimise Verb
- Optimize Verb
- Option Subst. Verb Adj.
- Oracle Subst. Verb Eigenn. Adj.
- Orange Adj. Subst. Verb
- Orate Verb
- Orb Subst. Verb Adj.
- Orbit Subst. Verb Adj. Part. Präs. Part. Perf.
- Orchestrate Verb Part. Perf. Part. Präs.
- Ordain Verb
- Ordeal Subst. Verb
- Order Subst. Verb Adj. Part. Perf.
- Ordinate Adj. Subst. Verb
- Organise Verb
- Organize Verb
- Organize around Verb
- Organized Adj. Part. Perf. Verb
- Orgasm Subst. Verb Adj.
- Orient Subst. Verb Adj. Eigenn.
- Orientalise Verb
- Orientalize Verb
- Orientate Verb Part. Perf. Part. Präs.
- Orientated Adj. Part. Perf. Verb
- Orienteer Subst. Verb
- Originate Verb
- Originate in Verb
- Ornament Subst. Verb Adj.
- Ornate Adj. Verb
- Orphan Subst. Verb Adj. Part. Perf.
- Orphrey Subst. Verb Adj.
- Orthogonalize Verb
- Orthonormalize Verb
- Orthophotograph Subst. Adj. Verb
- Oscillate Verb
- Osculate Verb
- Osmose Verb Subst.
- Ossify Verb
- Ostler Subst. Verb
- Ostracise Verb
- Ostracize Verb Part. Perf.
- Otter Subst. Adj. Verb
- Oubliette Subst. Verb
- Ought Verb
- Ought not Verb
- Oughter Verb