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.
His plan was thorough and detailed, leaving no loopholes.
Thanks to meticulous preparation, the event was a great success.
周到 means 'thorough' or 'scrupulous' on its own, but 周到綿密 adds the nuance of being detailed and exhaustive.
綿密 means 'detailed' or 'meticulous', while 周到綿密 combines this with the idea of covering all aspects thoroughly.
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.