1. 坚定的;坚信的;坚贞不渝的
If someone is steadfast in something that they are doing, they are convinced that what they are doing is right and they refuse to change it or to give up.

1. firm and dependable especially in loyalty

e.g. a steadfast ally
a staunch defender of free speech
unswerving devotion
unswerving allegiance

Synonym: staunchunswerving

2. marked by firm determination or resolution
not shakable

e.g. firm convictions
a firm mouth
steadfast resolve
a man of unbendable perseverence
unwavering loyalty

Synonym: firmsteadystiffunbendableunfalteringunshakableunwavering