- o.n.o.
- on oath
- on occasion
- on occasions
- on occasion(s)
- on off
- on-off
- on/off duty
- on offer
- on/off message
- on/off (the) air
- on/off the radar screen
- onomatopoeia
- onomatopoeian
- onomatopoeias
- onomatopoeic
- onomatopoeically
- onomatopoeic,onomatopoeical
- onomatopoeics
- onomatopoietic
- on-one-hands
- on one side
- on/onto the defensive
- on-our-part
- on pain of