involving beliefs, methods, etc. that are most common

mainline churches 主流教会

the rivalry between catalogue companies and mainline shops 目录公司和普通商店之间的竞争

relating to an important railway route between large towns or cities

Three mainline railway stations were closed because of bomb threats. 3个干线车站因炸弹威胁而关闭。

to inject (= put into the body through a needle) drugs directly into the blood

Several of her friends were mainlining heroin. 她有几个朋友注射海洛因。

By now she was mainlining. 她至今仍在注射毒品。