1. Marked by firm determination or resolution; not shakable
   "steadfast resolve";
   - firm, steady, stiff, unbendable, unfaltering, unshakable, unwavering, unshakeable
    
2. Firm and dependable especially in loyalty
   "a steadfast ally";
   - staunch, unswerving

See also: constant, resolute

Encyclopedia: Steadfast, Loyal and True