steadfast in WordNet English dictionary

1. marked by firm determination or resolution; not shakable
   "firm convictions"; "a firm mouth"; "steadfast resolve"; "a man of unbendable perseverence"; "unwavering loyalty"
   firm  steadfast  steady  stiff  unbendable  unfaltering  unshakable  unwavering 
   
2. firm and dependable especially in loyalty
   "a steadfast ally"; "a staunch defender of free speech"; "unswerving devotion"; "unswerving allegiance"
   steadfast  staunch  unswerving