Definition
to substitute for someone who usually performs a specific task or attends a specific meeting
替代某人執行職務；替某人參加會議
I had to sit in for my colleague during the meeting when he was absent due to illness.
我不得不在會議上代替我的同事，因為他因病缺席。
She kindly sat in for me during the class because I had other commitments.
她很好心地代替我上課，因為我有其他事情。
Please sit in for me at the board meeting if needed.
如果有需要，請代替我參加董事會會議。