There are multiple definitions:

1. outer diameter(English)

   • ID
   • Hemodynamics

2. overdose(English)

   • Toxicology

3. optical density(English)

   • Biophysics

4. Doctor of Optometry(English)

   • also as DO
   • Ophthalmology

5. optic disc(English)

   • CDR, OC, OSAL
   • Ophthalmology
   • https://doi.org…MI.2019.2899910

6. once daily(English)

   • omne in die (L)
   • HMDP, HTM, IOCM, IPD, LVOTO, RBM20, RVAD, SCN5A, S-ICD, TSAT
   • Pharmacology / pharmaceutics, Guidelines
   • https://doi.org…rheartj/ehab368

7. oculus dexter(Latin)

   • right eye (E)
   • ODS, OS, VOD
   • Ophthalmology

8. osseous dysplasia(English)

   • most common fibro-osseous lesion of the jaw affecting the periapical region
   • COD, FCOD
   • Dentistry
   • https://doi.org…2903-017-0455-5

9. open discectomy(English)

   • MID, VAD
   • Surgery, Pain, Spine (or spinal cord)
   • https://doi.org…12.1.SPINE11404

10. olfactory dysfunction(English)

    • BTT, COT, CRS, MOT, OD, PIOD, PVOD, TDI, URTI
    • Olfactory system
    • https://doi.org….1002/alr.22624

11. oocyte donation(English)

    • in this case the fetus can be completely allogeneic to the recipient. Consequently, the maternal immune system has to cope with greater immunogenetic dissimilarity compared to naturally conceived pregnancy
    • ED, HLA, NC, mPBMC
    • Gynecology, Pregnancy, Immunology
    • https://doi.org…jri.2019.103074

12. overdenture(English)

    • splinting of two interforaminal dental implants to support mandibular overdentures subjected to immediate load significantly reduces initial bone tissue strains experienced on the labial cortical bone in comparison with the use of unsplinted implants
    • ITV, RTV, ISQ
    • Dentistry, Biophysics, Prosthetics
    • https://pubmed.…h.gov/17340903/

13. optical depth(English)

    • the natural logarithm of the ratio of incident to transmitted radiant power through a material. Aka optical thickness
    • AOD
    • Optics and vision
    • http://burro.as…epthprimer.html

14. orphan drug(English)

    • the Orphan Drug Act (USA, 1983) established several incentives to encourage the development of these drugs to treat rare diseases and conditions
    • FDA, NME
    • Pharmacology / pharmaceutics, Legal issues
    • https://doi.org…/1750-1172-3-33

15. oxidized dextran(English)

    • refers to injectable conductive hydrogels as "smart" drug carrier with the properties of electro-responsiveness, pH-sensitivity, and inherent antibacterial activity
    • CP, Ph
    • Biomaterials, Pharmacology / pharmaceutics
    • https://doi.org…bio.2018.03.018

16. open defecation(English)

    • a widespread problem in the developing world
    • ODF, U5C
    • Hygiene, Pediatrics
    • https://doi.org…55/2018/4271915