everything; all matters (including all details); used to refer to all affairs or everything being in order.
引っ越しの準備は万事万端整った。
All the preparations for the move are complete.
出張のスケジュールは万事万端確認しておいてください。
Please check everything about the business trip schedule.
万事万端気をつけて行ってきてね。
Take care of everything and have a safe trip.