Not yet decided; undecided or pending (e.g., schedule or date to be determined).
次回の会合の日時は未定です。
The date and time of the next meeting are undecided.
開催場所は未定だが、決まり次第連絡します。
The venue is undecided, but we will inform you once it's decided.
報告書の提出日は未定のままになっている。
The submission date for the report remains undecided.