If you feel intimidated, you feel small, worried, and short of confidence because of the place you are in or the people around you. Maybe the room is full of older students, or a teacher seems very sure, or a job interview feels too big. It is about a feeling inside you, not about being hit or hurt. People use it in everyday talk; it is not slang and not especially formal. Though actually, speakers often stretch it: they say “I felt a bit intimidated” when they only mean shy or out of place, not truly scared. The feeling can come from a person or from a situation. The -ed ending tells you this is how someone feels.