1To give up completely; to abandon hopes or thoughts; to despair of something.
彼は受験を思い切ってあきらめ、就職する道を選んだ。
He gave up on taking the exam and chose to look for a job instead.
この案は現実的でないと判断して、思い切って断念した。
Judging that the plan wasn't realistic, I decisively abandoned it.
望みを思い切るのは簡単ではない。
It's not easy to give up one's hopes completely.
2To make up one's mind; to take a decisive, often bold decision; to muster the courage to do something.
転職を思い切って決め、面接の準備を始めた。
She made up her mind to change jobs and started preparing for interviews.
思い切ってプロポーズするつもりだ。
I'm going to take the plunge and propose.
もう迷わずに思い切ってやってみよう。
Don't hesitate any longer — go for it decisively.