Definitions for mainstayˈmeɪnˌsteɪ
Random House Webster's College Dictionary
a person or thing that acts as a chief support or part.
the stay that secures the mainmast forward.
Origin of mainstay:
a prominent supporter
"he is a pillar of the community"
anchor, mainstay, keystone, backbone, linchpin, lynchpin(noun)
a central cohesive source of support and stability
"faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
the forestay that braces the mainmast
A chief support.
A stabilising rope from the top of the mainmast to the bottom of the foremast.
the stay extending from the foot of the foremast to the maintop
main support; principal dependence