严密 (yán mì): tight; strict; closely controlled; rigorous and thorough

To ensure fairness in exams, the school established a strict invigilation system, with two teachers patrolling each exam room.

After a thorough investigation, the police finally found the hiding place of the criminal suspect.

The plan for this project is very well-structured, with tasks and deadlines for each phase clearly arranged.

Be careful! The security measures at this warehouse are extremely tight; no one can get in without a pass.