Main entry: mainstay
Definition: the forestay that braces the mainmast
Main entry: lynchpin, mainstay, keystone, linchpin, backbone, anchor
Definition: a central cohesive source of support and stability
Usage: faith is his anchor; the keystone of campaign reform was the ban on soft money; he is the linchpin of this firm
Definition: a prominent supporter
Usage: he is a pillar of the community