A cut off is the least mark that got a seat in a certain College for a certain entrance exam. For example, if you are appearing for NEET, the cut off is the least score that secured a seat in MBBS in a particular Colllege in a particular State. Now cut offs change every year depending on various factors such as no.of Candidates appearing for the exam, no.of Candidates qualified, top NEET score and difficulty of the exam.