Definition from Wiktionary, the free dictionary
mainstay (plural mainstays)
- A chief support.
- Agriculture is the mainstay of this country’s economy.
- Someone or something that can be depended on to make a regular contribution.
2016 May 23, Ignatiy Vishnevetsky, “Apocalypse pits the strengths of the X-Men series against the weaknesses”, in The Onion AV Club:
- X-Men: Apocalypse, directed by series mainstay Bryan Singer, gives Magneto, the Holocaust survivor who can control magnetic fields, and Xavier, the paraplegic telepath who tends to come off as really smug, next-to-zero shared screen time.
- (nautical) A stabilising rope from the top of the mainmast to the bottom of the foremast.
something that can be depended on to make a regular contribution
nautical: stabilizing rope