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to close up; to shut up (e.g. behind doors)
to cut off (e.g. because a deadline has expired); to close off (e.g. subscription list)
先着順で定員になったら締切ります。
Registration will be closed on a first-come basis once capacity is reached.
来月の申し込みを今週中に締切る。
Applications for next month will close this week.
投票を午後五時に締切ると発表された。
It was announced that voting would close at 5 PM.