1
to give up (all thoughts of);to abandon;to despair of
彼女の事が思い切れない。
I can't forget her.
2
to make up one's mind;to make a decision;to decide
重病には思い切った療法が必要だ。
Desperate diseases require desperate remedies.
Other forms
思いきる 【おもいきる】 (search-only kanji form)