| Oakem | n | Cockchafer |
| Oaken Bough Day | n | Oak Apple Day |
| Oar-cock | n | Water Rail |
| Oast | n | Malt-kiln |
| Oath | v | Swear |
| Oaves (1) | n | Eaves |
| Oaves (2) | n | Oat-chaff |
| Obedience | n | Curtsey |
| Obfusticated | adj | Obfuscated |
| Object | n | Deformed person |
| Obs-Bobs and Buttercups | int | Surprise, expression of |
| Occasion | n | Cause |
| Ochidore | n | Shore Crab |
| Ockshuns | n | Auctions |
| Oddy | adj | Vigorous |
| Offish | adj | Stand-offish |
| Oft | adv | Often |
| Oldness | n | Old age |
| Old-Land | n | Fallow land |
| Oliver | n | Elver |
| Ollet | n | Firewood |
| Omligus | n | Omnibus |
| Oncest | prep | Except |
| Onde | adj | Destined |
| Onion-Penny | n | Coin, Roman |
| Onker | n | Conkers (game) |
| Onliest | adj | Oddest |
| Onlight | v | Dismount |
| Onto | adj | Adjoining |
| Oonty | adj | Empty |
| Oose | n | Noose |
| Ooser | n | Mask, grotesque |
| Oozle (1) | v | Wheeze |
| Oozle (2) | n | Windpipe |
| Oozy | adj | Spongy |
| Ope | n | Opening |
| Open-Arse | n | Medlar |
| Or ever | prep | Before long |
| Or'n | pron | Either |
| Oration | n | Uproar |
| Orch | v | Gore |
| Orcheston Grass | phr | Creeping Bentgrass |
| Orchey | n | Orchis |
| Orchis Grass | n | Orchard Grass |
| Ordain | v | Discipline |
| Ore | n | Seaweed |
| Organ | n | Pennyroyal |
| Orloge | n | Clock |
| Ornified | adj | Adorned |
| Orra | pron | Either |
| Osier-Holt | n | Osier-Bed |
| Oss | v | Attempt |
| Oten | adv | Often |
| Other-Lucker | adj | Different |
| Otheren | adj | Alternate |
| Otherguess | adv | Different |
| Otherous | adv | Otherwise |
| Otherways | adv | Otherwise |
| Otherwhiles | adv | Occassionally |
| Otmoor Evil | n | Displaced Abomasum in Cattle |
| Ouchil | n | Slabwood |
| Ought | n | Zero |
| Ouks | int | Call to pigs |
| Out | v | Oust |
| Outdacious | adj | Audacious |
| Outlandish | adj | Foreign |
| Outlet | n | Pigsty, outdoor portion of |
| Outride | n | Commercial traveller |
| Outrider | n | Commercial traveller |
| Outrigger | n | Trailer (for wagon) |
| Outstand | v | Resist |
| Outward | adj | Immoral |
| Out-Ask | v | Publish banns for third time |
| Overcatch | v | Overtake |
| Overdrow | v | Overthrow |
| Overer | n | Mainlander |
| Overflush | adj | Superfluous |
| Overgo | v | Oversee |
| Overland | n | Land without farm buildings |
| Overlash | v | Strike forefoot with hind foot (of horse) |
| Overlayer | n | Trailer (for wagon) |
| Overlook | v | Bewitch |
| Overplush | n | Surplus |
| Overrathe | adj | Quick |
| Overrun | v | Escape |
| Overs | n | Riverbanks |
| Overseen | adj | Bewitched |
| Overshadow | v | Bewitch |
| Overstocked | adj | Having too much milk (of cow) |
| Overun | adj | From the mainland, not from the Isle of Wight |
| Overy | n | Causeway |
| Over-Night | n | Last night |
| Over-Runner | n | Shrew |
| Ovest | n | Acorns |
| Owlas | adj | Neglectful |
| Owling | v | Wassailing |
| Owlish | adj | Stupid |
| Owner | n | Ship owner (used as form of address) |
| Ownself | adj | Selfish |
| Oxer | n | Log, small |
| Oxey | adj | Mature |
| Oxford-Weed | n | Ivy-leaved Toadflax |
| Oyster (1) | n | Fir cone |
| Oyster (2) | n | Shoulder of veal |