締め切り (shimekiri) means “deadline”

More examples

締め切りまでに必要な書類をすべてそろえてください。shi me ki ri ma de ni hitsu yō na sho rui o su be te so ro e te ku da sa i

Please prepare all the necessary documents by the deadline.

Marks the point at which accepting something must stop, leaving no time for further submissions or applications.

期限kigen: The period allowed for completing a task or taking an action.
期日kijitsu: The date fixed for an event, payment, or required action.

定められた期日や時刻までに受け付けを終える期限。sada me ra re ta ki jitsu ya ji koku ma de ni u ke tsu ke o o e ru ki gen

締め切り (shimekiri) is the noun form of 締め切る (shimekiru, "close off"), combining 締める (shimeru, "close or tighten") with 切る (kiru, "cut off").

In Japanese notices, 締め切り (shimekiri) is often followed by 厳守 (genshu, "strict observance") to stress that late submissions are not accepted.