Definitions:

1. Abbreviation for 'Optical Density': the degree to which an object or material reduces the intensity of light passing through it. ABBREVIATION
   • Optical density (OD) measurement of bacterial cultures is a common technique used in microbiology.
2. An overdose of a drug, especially a fatal one. NOUN
   • America's 'OD' death rate is truly shocking when compared to the rest of the world's wealthy nations.

Synonyms:

• excess
• overdose
• oversupply
• surplus