Steadfast (adjective)

1. Remaining loyal and committed despite difficulties or temptations.
2. Firmly fixed in place; not moving or changing.

Origin:

Middle english: from old english stedefæst (see stead, fast).

Examples:

1. He was steadfast in his determination to succeed.
2. She was steadfast in her loyalty to her friends.
3. The company's steadfast commitment to customer service has led to its success.
4. He was steadfast in his support for the project.
5. The rock was steadfast and held the weight of the mountain.