ORMC - Pacinian corpuscle
- orodynia
- orofacial
- orofacial angle
- orofacial dyskinesia
- orofacial granulomatosis
- orofaciodigital syndrome type I
- orofaciodigital syndrome type II
- orofaciodigital syndrome type III
- orogastric
- orogastric tube
- orolingual
- oromandibular
- Oromandibular dystonia
- oromaxillary
- oromeningitis
- oronasal
- oronasal membrane
- oropharyngeal
- oropharyngeal airway
- oropharyngeal anthrax
- oropharyngeal dysphagia
- oropharyngeal isthmus
- oropharyngeal membrane
- oropharyngeal partition
- oropharyngeal tularemia
- Oropharynx
- Oropouche virus
- Oropsylla
- Oropsylla idahoensis
- Oropsylla montana
- Oropsylla silantiewi
- OROS
- orosomucoid
- orotate
- orotate phosphoribosyltransferase
- orotic acid
- orotic aciduria
- oroticaciduria
- orotidine
- orotidine-5‵