once - outp
- once-through boiler
- once-through forced flow
- once-through forced-flow boiler
- oncoming
- one above the other
- one set of stabilizers
- one, two, and three spindle jack
- one-armed
- one-axle trailer
- one-bayed
- one-bayed shed
- one-bayed shop
- one-cylinder engine
- one-dimensional
- one-headed rail
- one-layer
- one-layer winding
- one-level bill of materials
- one-line diagram
- one-line traffic
- one-man air drill
- one-man control
- one-off
- one-off part
- one-off production
- one-on-one nest stacking
- one-on-one nesting
- one-part
- one-part return idler
- one-piece
- one-ply
- one-point bearing
- one-point bridge support
- one-pole
- one-shift operation
- one-shot lubricator
- one-stage slip-on gearing
- one-stamp press
- one-storey
- one-story
