WordWeb Online

1. A prominent supporter
   "he is a mainstay of the community";
   - pillar
    
2. A central cohesive source of support and stability
   "faith is his mainstay";
   - anchor, keystone, backbone, linchpin, lynchpin
    
3. The forestay that braces the mainmast

Derived forms: mainstays

Type of: admirer, booster, champion, forestay, friend, protagonist, support, supporter

Encyclopedia: Mainstay