Dog Dictionary
- Obedience Trial
- Obesity
- Oblique Shoulders
- Obliquely Placed Eyes
- Occipital Protuberance
- Occiput
- Odd-Eyed
- Omnivore
- On-Dog Identification
- Open A/B
- Open Fontanel
- Open Junior
- Open Senior
- Ophthalmic
- Orange Belton
- Orthopedic Foundation for Animals (OFA)
- Osteoarthritis
- Osteochondrosis Dissecans (OCD)
- Osteosarcoma
- Otter Tail
- Out At The Elbows
- Out At The Shoulders
- Outcrossing
- Oval Chest
- Oval Eye
- Ovaries
- Overage Dam
- Overage Sire
- Overhang
- Overreaching
- Overshot
- Ovulate