much thought; deep consideration
Typically used in the set phrase 千慮の一失 (even a wise person sometimes makes a mistake) or 千慮の一得 (even a fool may sometimes give good counsel). Rarely used alone in modern Japanese.
Do you know the proverb 'Even a wise man sometimes makes a mistake'?
From Chinese 千慮 (qiān lǜ), literally 'a thousand considerations'. The exact historical derivation is uncertain; the spelling is conventionally associated with the meaning 'much thought'.