Being a re-applicant is not a weakness, rather, it is a strength. If you went through the admissions process and was not offered admission, the fact that you have chosen to re-apply means that you have grown since your initial application and have decided that despite not being offered admission that you want to try again for the sake of pursuing a medical education. To do this, you must reflect upon why you were not offered admission initially as other respondents have said. Furthermore, you must describe how you have grown since your previous application. If you have not, then you might consider taking more time to enhance your candidacy. This is a very personal question and is not something that can be generalizeable. Think about your strengths, weaknessess, and areas for improvement.