벼락치기를 하다
학교생활이랑 관련된 표현인 거 같은데, 무슨 뜻일까요? 공부 열심히 안 하는 거 아닌가요?

Question

Answer

You  "cram like crazy".

It is a very common expression among Korean students, as most of them do it one time or another, or every test time for some, in their school years. 
Korea is known for high academic pressures on the students, from kindergarten to college :-)

Answer

That means you study for an exam before a few days of the exam day. 
내일이 시험인데, 나는 벼락치기를 했다.