| Not only that | 13 |
| Not only that but also | 22 |
| Not opaque | 10 |
| Not open | 8 |
| Not open (to) | 13 |
| Not open now | 12 |
| Not open to the public | 22 |
| Not open, like a Broadway theater | 33 |
| Not open-ended | 14 |
| Not open-ended, as a question | 29 |
| Not openly | 10 |
| Not operating | 13 |
| Not operating properly | 22 |
| Not operator-assisted | 21 |
| Not opposed | 11 |
| Not opposed t' | 18 |
| Not opposin' | 16 |
| Not opt for mediocrity | 22 |
| Not opt. | 8 |
| Not optional | 12 |
| Not optional: Abbr. | 19 |
| Not oral | 8 |
| Not ordained | 12 |
| Not ordinary | 12 |
| Not ordinary: Abbr. | 19 |
| Not organized | 13 |
| Not orig. | 9 |
| Not original | 12 |
| Not original: Abbr. | 19 |
| Not originals | 13 |
| Not originals of letters, for short | 35 |
| Not ornate | 10 |
| Not ostensible | 14 |
| Not otherwise categorized (Abbr.) | 33 |
| Not otherwise classified (Abbr.) | 32 |
| Not our | 7 |
| Not ours | 8 |
| Not out | 7 |
| Not out and about | 17 |
| Not out of contention | 21 |
| Not out of it | 13 |
| Not out of one's mind | 25 |
| Not out of place | 16 |
| Not out of style? | 17 |
| Not out of the house | 20 |
| Not out of the question | 23 |
| Not out of the running | 22 |
| Not out of the sack | 19 |
| Not out of the sack yet | 23 |
| Not out on the town | 19 |
| Not out-of-bounds, as a ball | 28 |
| Not outdoors | 12 |
| Not outgoing | 12 |
| Not outright | 12 |
| Not outside | 11 |
| Not outsourced | 14 |
| Not outspoken | 13 |
| Not outstanding | 15 |
| Not outwardly | 13 |
| Not over | 8 |
| Not over the line | 17 |
| Not over the plate | 18 |
| Not over, under or around | 25 |
| Not overdone | 12 |
| Not overly emotional | 20 |
| Not overly friendly | 19 |
| Not overly titillating, usually | 31 |
| Not overseas | 12 |
| Not overspending | 16 |
| Not overwhelmed by | 18 |
| Not owing | 9 |
| Not own | 7 |
| Not own outright, with "on" | 37 |
| Not own, say | 12 |
| Not owned | 9 |
| Not owned, maybe | 16 |
| Not owners | 10 |
| Not packing | 11 |
| Not packing a rod | 17 |
| Not packing heat | 16 |
| Not paid by the hour | 20 |
| Not paid for, as factory work | 29 |
| Not paid hourly | 15 |
| Not paid up | 11 |
| Not palatable | 13 |
| Not pale, as a complexion | 25 |
| Not paleo- | 10 |
| Not panic | 9 |
| Not paraphrased | 15 |
| Not parked outdoors | 19 |
| Not part of a series | 20 |
| Not part of the leftovers | 25 |
| Not partake | 11 |
| Not partial | 11 |
| Not participate | 15 |
| Not participate in | 18 |
| Not participating, slangily | 27 |
| Not particular | 14 |
| Not particularly challenging | 28 |
| Not particularly friendly | 25 |