Premed is a mainly American school word, short for premedical. It can describe the classes that get a student ready for medical school — lots of biology, chemistry, physics — or the students taking those classes. You can say “a premed student,” “premed courses,” or, as a noun, “She is a premed.” It is campus talk: normal at a US university, a bit insider elsewhere. Though actually, it does not mean you are already in medical school; it means you are on the path, hoping to get in later. In Taiwan, students often enter medical school straight from high school, so this US stepping-stone does not map cleanly onto local school life. It is also not the same as premeditated, which is about planning a crime.