na-adjective, noun
scrupulous; careful; meticulous
Describes a person or action that is thorough and pays close attention to detail, often in planning or execution. Somewhat formal and less common in everyday speech than synonyms like 注意深い or 細心.
彼は周密な計画を立ててから仕事に取りかかる。
He starts work only after making a meticulous plan.
周密に調査を進めた結果、問題点が明らかになった。
As a result of proceeding with a scrupulous investigation, the issues became clear.
The word is composed of 周 (around, thorough) and 密 (dense, minute). The exact historical derivation is uncertain, but the combination suggests thoroughness and attention to detail.