An adverb meaning 'at the latest' — indicating that something will happen by a specified time and not later.
明日遅くとも午後3時には到着します。
I'll arrive by 3 PM at the latest tomorrow.
提出期限は遅くとも金曜日です。
The submission deadline is Friday at the latest.
会議は遅くとも30分で終わる予定だ。
The meeting is scheduled to finish within 30 minutes at the latest.
連絡は遅くとも明日の朝までにください。
Please contact me by tomorrow morning at the latest.