This is the 5002nd most frequent Japanese word.
締め切り
Deadline.
In this sentence, '締め切り' refers to a fixed term or deadline by which an action (submitting the report) must be completed.
レポートの締め切りは来週の金曜日です。
The deadline for the report is next Friday.
Here, '締め切り' describes the point in time that has elapsed, making it no longer valid for submissions.
締め切りが過ぎてしまったので提出できません。
Since the deadline has passed, I cannot submit it.
In this case, '締め切り' indicates a specific timeframe that is being considered for adjustment or extension.