- osannite
- oscillating bond
- oscillating function
- oscillation theory
- osmole
- osmophore
- ossein
- ostamer
- osteolite
- Ostwald process
- outbreak
- overheating
- overlap
- overlap welding
- overloaded
- overlying rock
- overlying strata
- overoxidize
- overpressure valve
- overproduction
- overrich mixture
- overshot guide
- overspeed preventer
- overthrust belt
- overthrust line
- overtight
- overwater
- overweight
- oxaluric acid
- oxidate
- oxidation film
- oxidation number
- oxidation rate
- oxidation retarder
- oxidation stability
- oxidation value
- oxidative catalyst
- oxidizability
- oxidized
- oxidized asphalt
- oxidized cellulose
- oxidized ore
- oxidizing
- oxidizing column
- oxidizing fusion
- oxidizing roasting
- oxidizing slag
- oxo process
- oxy-bitumen
- oxy-hydrogen
- oxyacetylene welding
- oxychloride
- oxygen absorption
- oxygen balance
- oxygen carrier
- oxygen cell
- oxygen cylinder
- oxygen mask
- oxygen value
- oxygenated
- oxygenation
- oxyhydrogen torch
- oxylith
- oxytetracycline
- oxytocic
- ozone resistance
- ozonization room
- Pachuca tank
- pack cloth
- pack wall
- packing ring
- packing space
- packless valve
- padding machine
- padouk
- paint base
- paint oil
- paint rock
- paint skin
- paired cylinder
- pale oil
- paleoclimatology
- paleogeographic map
- paleozoic
- pan amalgamation
- outride plating
- outsert moulding
- outshot
- outtake
- oven
- oven ageing
- oven wall
- over life
- overage
- overall dimension
- overestimate
- overflash
- overflow pipe
- overflow spring
- overflow valve