This is the 9374th most frequent Japanese word.
確固たる
"確固たる" means "firm, resolute, or unwavering."
Here, 確固たる means 'firm' or 'unwavering', describing his determination.
彼は確固たる意思を持って目標に向かっています。
He is moving towards his goal with firm determination.
In this sentence, 確固たる denotes 'solid' or 'stable', describing the financial foundation.
会社は確固たる財務基盤を築いています。
The company is building a solid financial foundation.
Here, 確固たる means 'firm' or 'strong' to describe her conviction.