1. Inject into the vein
   "She is mainlining heroin"

1. The principal route of a transportation system
   "The train stopped at all major stations along the main line"
    
2. [informal] Intravenous drug use or the vein used for injection
   "He developed health problems from years on the main line"

Derived forms: main lines, mainlining, mainlines, mainlined

Type of: inject, itinerary, path, route

Encyclopedia: Mainline