- IPA[ˌmān ˈlīn]
- a chief railroad line；a chief road or street.
- inject (a drug) intravenously
noun: main line, plural noun: main lines
- 1. a chief railroad line the crash blocked traffic on the main line a mainline station
- ▪ North American a chief road or street.
- 2. informal a principal vein as a site for a drug injection.
- 1. inject (a drug) intravenously Mariella mainlines cocaine five times a day he started mainlining on heroin