12 Letter Words That Start With 'O'

Find all the 12-letter words in the English language that start with O.

There are 155 12-letter words that begin with O.
There are 0 12-letter abbreviations that begin with O.
There are 86 12-letter phrases that begin with O.
Oblanceolate16 Obligational15 Obligatorily18 Obligingness16 Obliterating15 Obliteration14 Obscurantism18 Obscurantist16 Obsequiously26 Observations17 Observatorys20 Obsolescence18 Obsoleteness14 Obstetrician16 Obstreperous16 Obstructions16 Occasionally19 Occupational18 Oceanography23 Octogenarian15 Octosyllabic21 Octosyllable19 Oesophagitis18 Office-bearer22 Officeholder24 Officerships25 Officialness20 Oldfashioned20 Old-fashioned20 Oligarchical20 Oligodactyly22 Oligodendria15 Oligospermia17 Olive-colored18 Omnipresence18 One-billionth17 One-hundredth20 Oneiromancer16 One-millionth17 Onesidedness14 One-sixteenth22 One-upmanship21 Onlybegotten18 Onomatomania16 Onomatopoeia16 Onomatopoeic18 Onychophoran25 Oophorectomy24 Open-collared17 Ophthalmitis22 Opinionative17 Opisthotonos17 Opportunists16 Oppositeness16 Oppositional16 Oppressively22 Opsonisation14 Opsonization23 Optimisation16 Optimization25 Orchestrated18 Orchestrates17 Orchestrator17 Orchidectomy25 Ordinariness13 Organ-grinder15 Organicistic17 Organisation13 Organization22 Orientations12 Orienteering13 Ornamentally17 Ornithomimid20 Orphenadrine18 Orthodontics18 Orthodontist16 Orthodonture16 Orthogonally19 Orthographic23 Orthopaedics20 Orthopaedist18 Orthopedical20 Orthopedists18 Orthorhombic24 Orthotropous17 Oscillations14 Oscillograph20 Oscilloscope18 Osmoreceptor18 Ossification17 Ostentatious12 Osteomalacia16 Osteopathist17 Osteoporosis14 Osteosarcoma16 Osteostracan14 Otherworldly22 Otosclerosis14 Outbuildings16 Outlandishly19 Outmanoeuvre17 Out-migration15 Outnumbering17 Outperformed20 Outplacement18 Outrageously16 Outstretched18 Outstripping17 Outward-bound19 Overabundant18 Overachiever23 Overactivity23 Overburdened19 Overcapacity24 Overcautious17 Overcharging22 Overcritical19 Overcrossing18 Overcrowding22 Over-crowding22 Overdelicate18 Overdramatic20 Overemphasis22 Overestimate17 Overexertion22 Overexposure24 Overextended24 Overfamiliar20 Overgenerous16 Overinflated19 Overlordship21 Overmatching23 Overmuchness22 Overpopulate19 Overpopulous19 Overpowering21 Overpressure17 Overprinting18 Overproduced21 Overreaching21 Overreacting18 Overreaction17 Oversampling20 Overshadowed23 Overshooting19 Oversimplify25 Overspending19 Overstepping20 Overstocking22 Overstressed16 Overthrowing22 Overwhelming24 Overwintered19 Oxaloacetate21 Oxyacetylene27
Obiter Dictum Object Lesson Oblique Angle Oboe Da Caccia Observed Fire Obstacle Race Ocean Current Oceanic Abyss Ocean Sunfish Ockham's Razor Octane Number Octane Rating Ocular Muscle Oculus Dexter Odd-even Check Of Each Person Officer's Mess Off One's Guard Off The Record Off Your Guard Of The Essence Oil Geologist Oil Of Vitriol Old Fashioned Old Man's Beard Old School Tie Old Style Font Old Wives' Tale Omental Bursa Once In A While One Of The Boys One-way Street On The Average On The One Hand On The Qui Vive Onward Motion Open Fracture Opening Night Open Interval Open Marriage Open Sandwich Opera Comique Opera Company Opera Glasses Operatic Star Operator Gene Opposite Word Optative Mood Optical Bench Optical Crown Optical Fiber Optical Fibre Optical Flint Optical Glass Optical Maser Optical Prism Optic Chiasma Oral Contract Orange Balsam Orange Yellow Orbital Plane Orbital Point Orchard Grass Orchestra Pit Orchid Cactus Orchid Family Ordinary Care Organ Of Corti Oriental Sore Os Triquetrum Otic Ganglion Outdoor Sport Outdoor Stage Outer Garment Out Of Nothing Out Of The Blue Out Of Thin Air Out Of Wedlock Out Or Keeping Output Device Output Signal Overhand Knot Overnight Bag Oxytocic Drug Oyster Agaric Oyster Fungus