also: せんりょのいっしつ
noun
a slip by a wise person; a mistake even the cautious make
A yojijukugo meaning that even a person of great wisdom and care can make a small oversight. Often used to excuse a minor error or to note that nobody is perfect.
彼の失敗は千慮一失というべきだろう。
His mistake should be called a mere slip by a wise person.
千慮一失で、ベテラン社員が簡単なミスをした。
Even a veteran employee made a simple mistake, a case of a wise man's oversight.