1The final date or time by which something must be submitted or done; a deadline or cut-off. In forms and official writing the okurigana is often dropped (締切).
レポートの締め切りは今週末までです。
The deadline for the report is the end of this week.
締め切りに間に合わなくて、先生に謝った。
I couldn't make the deadline, so I apologized to the teacher.
応募が殺到したため、締め切りを早めることになった。
Applications flooded in, so they decided to move the deadline up.
願書の締切は3月10日必着です。
Applications must arrive by the March 10 deadline.
締め切り直前になると、いつも焦ってしまう。
I always panic right before a deadline.
2Closing a door, window, etc. completely so that a space is sealed off from the outside; the shut-up state. Sometimes written 閉め切り for this sense.
この部屋は締め切りで空気がこもっている。
This room has been shut up, so the air is stuffy.
長期の旅行中、家はずっと締め切りのままだった。
While we were away on a long trip, the house stayed shut up the whole time.
閉め切りの室内に車を停めると排気ガスがたまって危険だ。
Running a car in a closed-up space is dangerous because exhaust fumes build up.
3A cofferdam — a temporary structure built in civil or river engineering to hold back water so that work can be done in a dry area. Technical term.
ダム建設では川を締め切り、内部の水を抜いてから掘削する。
In dam construction they build a cofferdam to dam off the river, drain the water inside, and then excavate.