Definition
to be extremely busy or deeply involved in something
忙於某事，分身乏術
I've been up to my eyes in work lately, I really don't have time to go on vacation.
我最近忙於工作，真的沒有時間去度假。
During the final exam week, the students are all up to their eyes in studying.
在期末考試週，學生們都忙於學習。
Since taking over this project, she has been up to her eyes in work every day.
自從接手這個項目以來，她每天都忙於工作。