definition of
mainstay

[1] #1 mainstay n. [pillar] a prominent supporter; "he is a pillar of the community". wn

[2] #2 mainstay n. [anchor, keystone, backbone, linchpin, lynchpin] 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". wn

[3] #3 mainstay n. the forestay that braces the mainmast. wn