mainline vs prominent

mainline

adj
  • Normal, principal or standard. 

  • Of or pertaining to the principal route or line of a railway. 

  • Of or pertaining to a surface railway as distinct from an underground, elevated or light rail one. 

  • Of a sequence of opening moves: being part of a main line ("a standard sequence of opening moves considered to be best play"). 

verb
  • To integrate (code, etc.) into the main repository for a software project, rather than separate forks. 

  • To inject (a drug) directly into a vein. 

  • To consume voraciously. 

noun
  • In longline fishing the central line to which the branch lines with baits are attached. 

  • An airline's main operating unit, as opposed to codeshares or regional subsidiaries. 

  • The principal route or line of a railway. 

  • A principal vein into which a drug can be injected. 

  • The main repository for a software project, from which different versions (forks) may be split off. 

  • The pipeline carrying wastewater to the public drains or a septic tank. 

prominent

adj
  • eminent; distinguished above others 

  • standing out, or projecting; jutting; protuberant 

  • likely to attract attention from its size or position; conspicuous 

noun
  • Any of various moths having a conspicuous projection on the inner margin of the wings. 

  • In Nazi concentration camps, an inmate entrusted with minor supervisory duties and rewarded with perquisites. 

How often have the words mainline and prominent occurred in a corpus of books? (source: Google Ngram Viewer )