1. [US, informal] Research conducted on political opponents to gather potentially damaging information
   "The campaign team dug up some damaging oppo on their rival";
   - opposition research [US, informal]
    
2. [Brit, informal] A close colleague or partner, especially in the armed forces
   "He and his oppo have been through a lot together"
    
3. [Brit, informal] A person who holds a position equivalent to one's own in another organization, team, or context
   "The CEO met with her oppo from the rival company"; "My oppo in the Royal Navy had similar experiences";
   - opposite number

Derived forms: oppos

Encyclopedia: Oppo