- open fireopen fire synonyms
- open flash
- open fracture
- open frame
- open game
- openhandedopenhanded synonyms
- open-hearted
- open-hearth
- open-hearth furnace
- open-hearth process
- open-heart surgery
- open house
- open house, keep
- open housing
- openingopening synonyms
- opening nightopening night synonyms
- opening time
- open interval
- open-jaw
- open juncture
- open learning
- open letter
- open-line
- open loop
- open marketopen market synonyms
- open-market operations
- open marriageopen marriage synonyms
- open mic
- open mike
- open mind
- open-mindedopen-minded synonyms
- open-mouthedopen-mouthed synonyms
- opennessopenness synonyms
- open one's eyesopen one's eyes synonyms
- open one's heart to
- open one's mouthopen one's mouth synonyms
- open order
- open-pit
- open plan
- open policy
- open-pollinated
- open positionopen position synonyms
- open primaryopen primary synonyms
- open prison
- open punctuation
- open questionopen question synonyms
- open quote
- open-reel
- open-reel tape
- open registry
- open sandwich
- open seaopen sea synonyms
- open seasonopen season synonyms
- open season on
- open secretopen secret synonyms
- open sentenceopen sentence synonyms
- open sesameopen sesame synonyms
- open set
- open-shelf
- open shop
- open side
- open-sided
- open sight
- open slather
- open-source
- open spaceopen space synonyms
- open-stack
- open stance
- open-standard
- open stock
- open string
- open system
- open texture
- open the door to
- open-timbered
- open trailer
- open union
- open universeopen universe synonyms
- Open University
- open upopen up synonyms
- open verdict
- open-web
- open with
- openworkopenwork synonyms
- OPer.
- operaopera synonyms
- operableoperable synonyms
- opéra bouffe
- opera buffaopera buffa synonyms
- opera cloak
- opéra comique
- opera glassesopera glasses synonyms
- operagoer
- opera hatopera hat synonyms
- opera houseopera house synonyms
- operand
- operantoperant synonyms
- operant conditioning
- operant learning
- opera seria
- operateoperate synonyms
- operaticoperatic synonyms
- operatingoperating synonyms
- operating budgetoperating budget synonyms
- operating income
- operating roomoperating room synonyms
- operating systemoperating system synonyms
- operating tableoperating table synonyms
- operating theatre
- operationoperation synonyms
- operationaloperational synonyms
- operational amplifier
- operational calculus
- operationalism
- operationalize
- Operation Barbarossa
- Operation Desert Storm
- Operation Overlord
- Operation Sealion
- operations researchoperations research synonyms
- operations room
- operativeoperative synonyms
- operatize
- operatoroperator synonyms
- operatory
- opera window
- opercle
- operculate
- operculum
- opere citato
- operetta
- operon
- operoseoperose synonyms
- opgefok
- Ophelia
- Opheltes
- ophicleide
- ophidianophidian synonyms
- ophidiid
- ophiolatry
- ophiolite
- ophiolite suite
- ophiology
- ophiophagous
- Ophir
- ophite
- ophitic
- Ophiuchus
- ophiuroid
- ophthal.
- ophthalm-
- ophthalmia
- ophthalmia neonatorum
- ophthalmicophthalmic synonyms
- ophthalmic optician
- ophthalmitis
- ophthalmo-
- ophthalmodynamometer
- ophthalmol.
- ophthalmologistophthalmologist synonyms
- ophthalmology
- ophthalmometer
- ophthalmoscope
- ophthalmoscopy
- Ophüls
- opiateopiate synonyms
- opiatic
- opineopine synonyms
- opinedopined synonyms
- opinicus
- opinionopinion synonyms
- opinionatedopinionated synonyms
- opinionativeopinionative synonyms
- opinioned
- opinion pollopinion poll synonyms
- opioid
- opioid epidemic
- opistho-
- opisthobranch
- opisthodomos
- opisthognathous
- opisthograph
- opisthosoma
- opiumopium synonyms
- opium den
- opiumism
- opium poppy
- Opium War
- Opium Wars
- OPM
- Opole
- Oporto
- opossumopossum synonyms
- opossum block
- opossum shrimp
- opotherapy
- opp.
- Oppenheim
- Oppenheimer
- Oppenheimer, J. Robert
- oppidanoppidan synonyms
- oppilate
- oppo
- opponency
- opponentopponent synonyms
- opportuneopportune synonyms
- opportunismopportunism synonyms
- opportunistopportunist synonyms
- opportunisticopportunistic synonyms
- opportunistic infection
- opportunityopportunity synonyms
- opportunity cost
- opportunity shop
- opposable
- opposable thumb
- opposeoppose synonyms
- opposedopposed synonyms
- opposed-cylinder
- opposed-piston engine
- opposeless
- oppositeopposite synonyms
- opposite field
- opposite numberopposite number synonyms
- opposite prompt
- opposite sex
- oppositionopposition synonyms
- oppositionaloppositional synonyms
- oppositional defiant disorder
- oppositionistoppositionist synonyms
- opposition research
- oppressoppress synonyms
- oppressedoppressed synonyms
- oppressionoppression synonyms
- oppressiveoppressive synonyms
- oppressoroppressor synonyms
- opprobriousopprobrious synonyms
- opprobriumopprobrium synonyms
- oppugnoppugn synonyms
- oppugnantoppugnant synonyms
- OPRA
- opry
- Ops
- op-shop
- opsimath
- opsin
- opsonic
- opsonic index
- opsonify
- opsonin
- opsonize
- optopt synonyms
- optative
- optedopted synonyms
- opticoptic synonyms
- opticaloptical synonyms
- optical activity
- optical art
- optical astronomy
- optical bench
- optical binary
- optical center
- optical character reader
- optical character recognitionoptical character recognition synonyms
- optical computer
- optical crown
- optical density
- optical discoptical disc synonyms
- optical diskoptical disk synonyms
- optical double star
- optical effectsoptical effects synonyms
- optical fiberoptical fiber synonyms
- optical fibre
- optical flint
- optical glass
- optical illusionoptical illusion synonyms
- optical isomer
- optical isomerism
- optical mark reading
- optical maser
- optical microscope
- optical mouse
- optical path
- optical printer
- optical pumping
- optical pyrometer
- optical resonator
- optical rotation
- optical scanner
- optical scanningoptical scanning synonyms
- optical sound
- optical soundtrack
- optical tooling
- optical tweezers
- optical wedge
- optic axis
- optic chiasma
- optic disc
- optician
- opticist
- optic nerve