There are multiple definitions:

1. oxygen-dependent degradation(English)

   • Oxygen
   • https://doi.org…4814/phy2.70648

2. Ouchterlony double diffusion(English)

   • one of the simplest techniques extensively used to check antisera for the presence of antibodies for a particular Ag and to determine its titer
   • Ag
   • Immunology, Clinical chemistry
   • https://vlab.am…m=638&cnt=1

3. orphan drug designation(English)

   • Pharmacology / pharmaceutics

4. oppositional defiant disorder(English)

   • ADHD, GAD, OCD, PTSD, LPE
   • Psychology
   • https://doi.org…787-020-01696-0