one- - over
- ore-handling bridge
- ore-loading crane
- ore-roasting kiln
- ore-roasting plant
- ore-smelting furnace
- ore-storage bunker
- ore-washing plant
- oreing-down
- oreless boil
- organ-pipe bin
- organ-pipe bunker
- organic coated electrode
- organic coating
- orientation
- orientation density
- orientation dependence
- orientation of single crystals
- orientation polarization
- orientation texture
- orientation texture pattern
- oriented silicon iron
- orifice
- orifice area
- orifice spud
- orifice washer
- original area
- original austenite
- original austenite grain
- original austenite grain boundaries
- original beam
- original constituent
- original crack size
- original crystals
- original gauge length
- original radiation
- original stock
- original substance
- ornamental casting
- ornamental molding
- orpiment