Third-person singular simple present indicative form of mainline.(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "mainlines" in a sentence
"One mainlines heroin and the other spends taxpayer money."
"Cable news starts with a story, removes the grain and nuance then mainlines the fury."
"There used to be a railway line, linking with mainlines at Yatton in the north and Witham in the south, to transport produce – notably Cheddar strawberries – from these fields to market, but it closed in 1965, and along its route there is now an eight-mile traffic-free way for cyclists and walkers called the Strawberry Line."