12-Letter Words Starting with O

All 108 twelve-letter words that start with O

OB

• objectifying30n. Objectification.
• oblanceolate16adj. Of a reversed lanceolate shape: attached to the stem by the pointed...
• obligatorily18adv. In an obligatory manner.
• obliterating15adj. Causing obliteration; devastating.
• obliteration14n. The total destruction of something.
• obscurantism18n. A state of opposition to human progress or enlightenment.
• obscurantist16n. A practitioner of obscurantism; an obscurant.
• obsequiously26adv. In an obsequious manner.
• obsolescence18n. The state of being obsolete—no longer in use; gone into disuse; disused...
• obstetrician16n. A physician who specializes in childbirth.
• obstreperous16adj. Attended by, or making, a loud and tumultuous noise; boisterous.

OC

• occasionally19adv. On occasion: at relatively infrequent intervals, from time to time...
• occupational18adj. Of, belonging, or relating to an occupation (in any sense).
• oceanography23n. The exploration and scientific study of the oceans and ocean floor.
• octogenarian15n. Synonym of eightysomething: a person between 80 and 89 years old.
• octosyllabic21adj. Containing eight syllables.

OD

• odontologist14n. A specialist in odontology.

OF

• officeholder24n. A person who holds an office, especially one appointed or elected to a...

OL

• oligarchical20adj. Oligarchic.
• oligopeptide18n. A peptide containing a relatively small number of amino acids.
• oligospermia17n. Low concentration of sperm in semen.
• oligotrophic20adj. Deficient in nutrition (providing little nourishment).

OM

• ombudsperson19n. Synonym of ombudsman.
• omnipresence18n. The ability to be, or the characteristic of being, at all places at the...
• omnishambles21n. A situation that is bad or mismanaged in every way.

ON

• onomatopoeia16n. The property of a word that sounds like what it represents.
• onomatopoeic18adj. Of or relating to onomatopoeia.

OO

• oophorectomy24n. The surgical removal of one or both ovaries, usually performed to treat...

OP

• operatically19adv. In an operatic manner.
• oppositional16adj. Of, pertaining to, or exhibiting opposition.
• oppressively22adv. In an oppressive manner.
• optimization25n. The design and operation of a system or process to make it as good as...
• optogenetics17n. A science that combines optics and genetics, aiming at controlling...

OR

• orchestrator17n. One who orchestrates.
• orchidaceous20adj. Of or pertaining to orchids.
• ordinariness13n. The quality or condition of being ordinary.
• organisation13n. Non-Oxford British English and Australian standard spelling of...
• organization22n. The quality of being organized.
• organoleptic17adj. Of or pertaining to the sensory properties of a particular food or...
• organosulfur16adj. Describing any of a series of derivatives of sulfur that have at least...
• orienteering13n. The act of racing across unfamiliar place using a map and compass.
• ornamentally17adv. In an ornamental way.
• orthodontics18n. A specialty of dentistry concerned with correcting misalignment of...
• orthodontist16n. An orthodontic dentist.
• orthognathic21adj. Straight-jawed.
• orthogonally19adv. In an orthogonal manner; perpendicularly; at right angles.
• orthographic23adj. Of a projection used in maps, architecture etc., in which the rays are...
• orthorhombic24adj. Having three unequal axes at right angles.

OS

• oscilloscope18n. An electronic measuring instrument that creates a visible...
• ossification17n. The normal process by which bone is formed.
• ostentatious12adj. Of ostentation.
• osteoblastic16adj. Of or pertaining to an osteoblast.
• osteogenesis13n. The formation and development of bone.
• osteological15adj. Of or relating to osteology.
• osteomalacia16n. A softening of adult bones due to inadequate mineralization; the adult...
• osteoporosis14n. A disease, occurring especially in women following menopause, in which...
• osteoporotic16adj. Relating to osteoporosis.
• osteosarcoma16n. A type of cancer of the bone.

OT

• otherworldly22adj. Of, concerned with, or preoccupied with a world different from the...
• otosclerosis14n. Sclerosis of the tissues of the labyrinth and middle ear.

OU

• outlandishly19adv. In an outlandish manner.
• outmanoeuvre17v. To perform manoeuvres or movements more successfully or better than; to...
• outmigration15n. Synonym of emigration.
• outplacement18n. The process of helping to find new employment for redundant workers...
• outrageously16adv. In an outrageous manner; to an outrageous degree.
• outstandings14n. Outstanding amounts; unpaid debts.
• outstretched18adj. Extended or stretched out.
• outstripping17n. The act or process of something being outstripped.

OV

• overabundant18adj. Excessively abundant.
• overachiever23n. One who overachieves; one who has too much success.
• overactivity23n. Excessive activity.
• overburdened19adj. Excessively burdened.
• overcapacity24n. A capacity for the production of a commodity or product that is in...
• overcautious17adj. Excessively cautious.
• overcharging22n. The act or process of charging excessively.
• overclocking24n. An instance or incident of processor (CPU), or any electronic logic...
• overcritical19adj. Excessively critical.
• overcrowding22n. The situation where a space holds more occupants than it can...
• overdesigned18adj. Having undergone excessive design, leading to complicatedness or an...
• overdramatic20adj. Dramatic to excess.
• overeducated19adj. Having received too much education.
• overemphasis22n. Excessive emphasis.
• overestimate17v. To judge or calculate too highly.
• overexertion22n. Excessive exertion; so much exertion that discomfort or injury results.
• overexposure24n. Excessive exposure.
• overextended24adj. Extended or expanded beyond a safe limit.
• overgenerous16adj. Generous to an excessive degree.
• overinflated19adj. Inflated; exaggerated.
• overlordship21n. The position or quality of being an overlord.
• overpainting18n. Something painted over the top of something else.
• overpopulate19v. To fill with too many individuals; to exceed the capacity of a region...
• overpowering21adj. That overpowers; so strong as to be overwhelming.
• overpressure17n. Excess or markedly elevated pressure, especially a transient high...
• overreaching21adj. That overreaches (all senses).
• overreaction17n. A reaction that is excessive.
• overreliance17n. Excessive reliance.
• oversampling20n. The act of one who oversamples.
• overshadowed23adj. Superseded by, covered up by, overtaken or eclipsed.
• oversimplify25v. To explain or present something in a way that excludes important...
• overspeeding19adj. Travelling at an excessive speed.
• overspending19n. The spending of too much money.
• overstocking22n. A stocking intended to be worn over another stocking.
• overstressed16adj. Excessively stressed.
• overthinking23n. The act of thinking too much about something.
• overwhelming24adj. Overpowering, staggering, or irresistibly strong.

OX

• oxaloacetate21n. Any salt or ester of oxaloacetic acid.
• oxoglutarate20n. Any salt or ester of oxoglutaric acid.
• oxyacetylene27n. A mixture of oxygen and acetylene, which burns at a high temperature...

Questions about these words

How many twelve-letter words that start with O are there?

Word.ws lists 108 twelve-letter words that start with O, plus 1,101 rare ones.

What are common twelve-letter words that start with O?

organization, occasionally, organisation, overwhelming, occupational, optimization, overshadowed and overcrowding.

Which of the twelve-letter words that start with O has the highest letter score?

objectifying scores 30 points with the standard letter tile values.

Related word lists

• 12-Letter Words
• Words That Start with O
• 11-Letter Words Starting with O
• 13-Letter Words Starting with O
• Q Words Without U