noun, na-adjective
thorough and detailed; meticulous; scrupulously complete
Emphasizes that every detail has been carefully considered and nothing has been overlooked. Often used to describe plans, preparations, or investigations.
彼の計画は周到綿密で、抜け目がなかった。
His plan was thorough and detailed, leaving no loopholes.
周到綿密な準備のおかげで、イベントは大成功だった。
Thanks to meticulous preparation, the event was a great success.
A yojijukugo (four-character compound) combining 周到 (thorough, scrupulous) and 綿密 (detailed, meticulous). The exact historical derivation is uncertain, but it is a natural pairing of two near-synonyms to intensify the meaning.