Doing something single-mindedly or earnestly, with intense focus and without distraction.
彼はゴールに向かってひたすら走り続けた。
He kept running toward the goal with single-minded determination.
合格を目指してひたすら勉強した。
I studied earnestly (single-mindedly) to pass the exam.
彼女はひたすら謝り続けた。
She just kept apologizing over and over.